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Conservation of energy means energy cannot be created or destroyed, although it can be transferred between stores."},{"text":"Energy is measured in watts (W) and cannot be created or destroyed.","correct":false,"explanation":"Watts measure power, which is the rate of energy transfer. Energy itself is measured in joules (J) and cannot be created or destroyed."},{"text":"Energy is measured in joules (J) and cannot be transferred between stores.","correct":false,"explanation":"Energy can be transferred between stores by forces, currents, heating or waves. It is measured in joules and cannot be created or destroyed."},{"text":"Energy is measured in newtons (N) and cannot be created or transferred.","correct":false,"explanation":"Newtons measure force rather than energy, and energy can be transferred. Energy is measured in joules and cannot be created or destroyed."}]},{"id":"d7c168d8-87ea-4a45-80bf-69624f0e1022","cardType":"basic","points":1,"front":"Which energy store does a moving object have?","back":"Kinetic energy store.","mcqOptions":[{"text":"Kinetic energy store.","correct":true,"explanation":"A moving object has energy in its kinetic energy store. This store becomes larger when the object’s mass or speed increases."},{"text":"Gravitational potential energy store.","correct":false,"explanation":"Gravitational potential energy depends on an object’s position in a gravitational field, not simply its motion. A moving object has a kinetic energy store."},{"text":"Elastic strain energy store.","correct":false,"explanation":"Elastic strain energy is stored when an elastic object is stretched or compressed. Motion gives an object energy in its kinetic energy store."},{"text":"Internal energy store.","correct":false,"explanation":"Internal energy is associated with the particles within an object and often changes during heating. A moving object instead has a kinetic energy store."}]},{"id":"4b036e2f-a7c9-4e98-b0dc-44b5310e82a0","cardType":"basic","points":1,"front":"Which energy store increases when an object is lifted higher?","back":"Gravitational potential energy store.","mcqOptions":[{"text":"Gravitational potential energy store.","correct":true,"explanation":"Lifting an object transfers energy to its gravitational potential energy store. The increase is greater for a larger mass or a greater change in height."},{"text":"Kinetic energy store.","correct":false,"explanation":"Kinetic energy depends on speed, so lifting an object does not necessarily increase it. Greater height increases the object’s gravitational potential energy store."},{"text":"Elastic strain energy store.","correct":false,"explanation":"Elastic strain energy increases when an elastic object is stretched or compressed. Raising an object increases its gravitational potential energy store instead."},{"text":"Electrostatic energy store.","correct":false,"explanation":"Electrostatic energy concerns separated or arranged electric charges, not an object’s height. Lifting increases the object’s gravitational potential energy store."}]},{"id":"38404670-6406-4f8c-b043-9cac674e5d12","cardType":"basic","points":1,"front":"Which energy store decreases in a battery-powered torch as it runs?","back":"Chemical energy store.","mcqOptions":[{"text":"Chemical energy store.","correct":true,"explanation":"A battery stores energy chemically. As the torch operates, energy is transferred electrically from the battery, so its chemical energy store decreases."},{"text":"Internal energy store.","correct":false,"explanation":"The battery may warm slightly, but its main decreasing store is not internal energy. The torch is powered by energy transferred from the battery’s chemical store."},{"text":"Electrostatic energy store.","correct":false,"explanation":"The battery creates a potential difference, but its energy is principally stored chemically rather than as separated static charges. Its chemical energy store decreases during operation."},{"text":"Nuclear energy store.","correct":false,"explanation":"A torch battery releases energy through chemical reactions, not changes in atomic nuclei. Therefore, it is the chemical energy store that decreases."}]},{"id":"cababb89-b538-4004-b1f7-b4a2a03eb73c","cardType":"basic","points":1,"front":"Which energy store is involved when a spring is compressed?","back":"Elastic strain energy store.","mcqOptions":[{"text":"Elastic strain energy store.","correct":true,"explanation":"Compressing a spring changes its shape and transfers energy to its elastic strain energy store. The spring can release this energy when it returns to its original shape."},{"text":"Gravitational potential energy store.","correct":false,"explanation":"Gravitational potential energy changes when an object’s height changes. Compressing a spring instead transfers energy to the spring’s elastic strain energy store."},{"text":"Chemical energy store.","correct":false,"explanation":"Chemical energy is associated with substances such as fuels, foods and batteries. A compressed spring stores energy in its elastic strain energy store."},{"text":"Kinetic energy store.","correct":false,"explanation":"Kinetic energy belongs to moving objects, whereas a compressed spring can be stationary. Its changed shape gives it an elastic strain energy store."}]},{"id":"c92be0d7-5db3-40c5-a13c-1859ef3c3460","cardType":"cloze","points":null,"front":"Energy stored in atomic nuclei is the [ ]; energy due to separated or arranged charges is the [ ].","back":"Energy stored in atomic nuclei is the nuclear energy store; energy due to separated or arranged charges is the electrostatic energy store.","mcqOptions":[{"text":"Energy stored in atomic nuclei is the nuclear energy store; energy due to separated or arranged charges is the electrostatic energy store.","correct":true,"explanation":"The nuclear store holds energy associated with atomic nuclei. The electrostatic store holds energy associated with the positions and arrangement of electric charges."},{"text":"Energy stored in atomic nuclei is the chemical energy store; energy due to separated or arranged charges is the electrostatic energy store.","correct":false,"explanation":"Chemical energy concerns arrangements of atoms and chemical bonds, not energy within atomic nuclei. Energy stored in nuclei belongs to the nuclear energy store."},{"text":"Energy stored in atomic nuclei is the nuclear energy store; energy due to separated or arranged charges is the magnetic energy store.","correct":false,"explanation":"Magnetic energy is associated with magnetic fields, not separated electric charges. Arranged or separated charges have energy in the electrostatic energy store."},{"text":"Energy stored in atomic nuclei is the internal energy store; energy due to separated or arranged charges is the chemical energy store.","correct":false,"explanation":"Internal energy concerns particle motion and interactions, while chemical energy concerns bonds. Nuclei use the nuclear store, and separated charges use the electrostatic store."}]},{"id":"9eaa782b-d399-4b87-b6c4-841ec4c7d863","cardType":"basic","points":1,"front":"When energy is transferred by heating, which store usually increases?","back":"Internal energy store.","mcqOptions":[{"text":"Internal energy store.","correct":true,"explanation":"Heating transfers energy into an object’s internal energy store. This generally raises its temperature or causes a change of state without increasing temperature."},{"text":"Kinetic energy store.","correct":false,"explanation":"Although heated particles move more rapidly, the macroscopic energy store is called internal energy, not kinetic energy. Heating usually increases the object’s internal energy store."},{"text":"Chemical energy store.","correct":false,"explanation":"Chemical energy changes during chemical reactions rather than ordinary heating. Energy transferred by heating usually increases the receiving object’s internal energy store."},{"text":"Elastic strain energy store.","correct":false,"explanation":"Elastic strain energy increases through stretching or compression, not heating. Heating usually transfers energy into an object’s internal energy store."}]},{"id":"b2a0e86e-6c67-4df5-bbac-7fba9fa067fe","cardType":"cloze","points":null,"front":"Energy is [ ] kinetic, chemical or gravitational potential; energy is [ ] forces, currents, heating or waves.","back":"Energy is stored as kinetic, chemical or gravitational potential; energy is transferred by forces, currents, heating or waves.","mcqOptions":[{"text":"Energy is stored as kinetic, chemical or gravitational potential; energy is transferred by forces, currents, heating or waves.","correct":true,"explanation":"Kinetic, chemical and gravitational potential describe energy stores. Forces, electric currents, heating and waves are pathways by which energy is transferred between stores."},{"text":"Energy is transferred by kinetic, chemical or gravitational potential; energy is stored as forces, currents, heating or waves.","correct":false,"explanation":"This reverses stores and transfer pathways. Energy is stored as kinetic, chemical or gravitational potential energy and transferred by forces, currents, heating or waves."},{"text":"Energy is conserved as kinetic, chemical or gravitational potential; energy is transferred by forces, currents, heating or waves.","correct":false,"explanation":"Conservation describes the total amount of energy, not how energy exists in a system. Energy is stored as kinetic, chemical or gravitational potential energy."},{"text":"Energy is stored as kinetic, chemical or gravitational potential; energy is measured by forces, currents, heating or waves.","correct":false,"explanation":"Forces, currents, heating and waves are transfer pathways, not methods of measurement. Energy is transferred by these pathways and measured in joules."}]},{"id":"90be9b89-bc82-4659-a12e-25bfbeebb393","cardType":"basic","points":1,"front":"What transfer pathway occurs when a force moves an object?","back":"Mechanical work done.","mcqOptions":[{"text":"Mechanical work done.","correct":true,"explanation":"A force transfers energy mechanically when it causes an object to move through a distance. This transfer pathway is described as mechanical work being done."},{"text":"Electrical work done.","correct":false,"explanation":"Electrical work involves energy transferred by moving charges in a circuit, not simply by a force moving an object. The correct pathway is mechanical work done."},{"text":"Heating by conduction.","correct":false,"explanation":"Conduction transfers energy because of a temperature difference through particle interactions. When a force moves an object, the transfer pathway is mechanical work done."},{"text":"Electromagnetic wave transfer.","correct":false,"explanation":"Electromagnetic waves transfer energy through radiation, such as visible light or infrared. A force moving an object transfers energy by mechanical work done."}]},{"id":"6a8dc410-ef7a-4293-a58d-9d84fcc76436","cardType":"basic","points":2,"front":"For a falling ball with negligible air resistance, which store-to-store transfer occurs?","back":"Gravitational potential store → kinetic store.","mcqOptions":[{"text":"Gravitational potential store → kinetic store.","correct":true,"explanation":"As the ball falls, its height decreases and its speed increases. Energy is therefore transferred from its gravitational potential store to its kinetic store."},{"text":"Kinetic store → gravitational potential store.","correct":false,"explanation":"This reversed transfer occurs when an object rises and slows down. A falling ball speeds up, so energy moves from its gravitational potential store to its kinetic store."},{"text":"Gravitational potential store → internal store.","correct":false,"explanation":"This assumes the ball’s energy is dissipated as heating. With negligible air resistance, energy is transferred instead from the gravitational potential store to the kinetic store."},{"text":"Elastic potential store → kinetic store.","correct":false,"explanation":"An elastic potential store supplies energy when a stretched or compressed object returns towards its original shape. A falling ball transfers energy from its gravitational potential store to its kinetic store."}]},{"id":"3b17326d-3f56-41d6-8194-913b08202e06","cardType":"basic","points":1,"front":"What transfer pathway occurs when a current flows in a circuit?","back":"Electrical work done.","mcqOptions":[{"text":"Electrical work done.","correct":true,"explanation":"A current consists of moving charges, which transfer energy from a power supply to circuit components. This transfer pathway is described as electrical work done."},{"text":"Mechanical work done.","correct":false,"explanation":"Mechanical work requires a force to move an object through a distance. Energy transferred by moving charges in a circuit is described as electrical work done."},{"text":"Heating by conduction.","correct":false,"explanation":"Components may become hot after receiving energy, but conduction is not the pathway associated with current itself. Moving charges transfer energy by electrical work done."},{"text":"Electromagnetic wave transfer.","correct":false,"explanation":"Electromagnetic waves can carry energy away from some circuit components, but current transfers energy through the circuit by electrical work done."}]},{"id":"a5f4e3f1-e330-4af4-b6cf-4480c5ae148f","cardType":"basic","points":1,"front":"In a torch, by what pathway is visible light transferred from the lamp?","back":"Electromagnetic waves.","mcqOptions":[{"text":"Electromagnetic waves.","correct":true,"explanation":"Visible light is part of the electromagnetic spectrum. Energy leaving the torch lamp as visible light is therefore transferred by electromagnetic waves."},{"text":"Mechanical vibrations.","correct":false,"explanation":"Mechanical vibrations transfer sound through particles in a medium, not visible light. Light from the lamp transfers energy through electromagnetic waves."},{"text":"Electrical currents.","correct":false,"explanation":"Electrical current transfers energy to the lamp within the torch circuit. Once emitted as visible light, the energy travels away through electromagnetic waves."},{"text":"Thermal conduction.","correct":false,"explanation":"Thermal conduction transfers energy through particle interactions in matter and requires direct contact. Visible light from the lamp is transferred by electromagnetic waves."}]},{"id":"2155660c-6ac6-4ce7-b18a-5948b576f303","cardType":"cloze","points":null,"front":"Friction often transfers energy to [ ] of the [ ].","back":"Friction often transfers energy to internal energy stores of the surroundings.","mcqOptions":[{"text":"Friction often transfers energy to internal energy stores of the surroundings.","correct":true,"explanation":"Friction causes interacting surfaces and nearby material to heat up. It therefore transfers energy into the internal energy stores of the surroundings."},{"text":"Friction often transfers energy to kinetic energy stores of the surroundings.","correct":false,"explanation":"Friction usually reduces motion rather than increasing the surroundings’ kinetic stores. The dissipated energy is transferred to the internal energy stores of the surroundings."},{"text":"Friction often transfers energy to nuclear energy stores of the surroundings.","correct":false,"explanation":"Ordinary friction does not alter atomic nuclei, so it cannot increase nuclear energy stores. It heats materials, increasing the internal energy stores of the surroundings."},{"text":"Friction often transfers energy to internal energy stores of the gravitational field.","correct":false,"explanation":"A gravitational field is associated with gravitational potential energy, not an internal energy store. Friction increases the internal energy stores of the surroundings."}]},{"id":"de218006-0178-4bce-870e-217e199a1c69","cardType":"cloze","points":null,"front":"In a closed system, total energy stays [ ] because no energy [ ].","back":"In a closed system, total energy stays constant because no energy enters or leaves.","mcqOptions":[{"text":"In a closed system, total energy stays constant because no energy enters or leaves.","correct":true,"explanation":"A closed system cannot exchange energy with its surroundings. Energy may move between stores inside it, but its total energy remains constant."},{"text":"In a closed system, total energy stays decreasing because no energy enters or leaves.","correct":false,"explanation":"Energy does not disappear when it becomes less useful or is dissipated. Because none enters or leaves a closed system, its total energy stays constant."},{"text":"In a closed system, total energy stays increasing because no energy enters or leaves.","correct":false,"explanation":"Preventing energy exchange does not cause energy to accumulate. Since no energy enters or leaves a closed system, its total energy stays constant."},{"text":"In a closed system, total energy stays constant because no energy moves between stores.","correct":false,"explanation":"Energy can still be transferred between stores within a closed system. Total energy stays constant specifically because no energy enters or leaves the system."}]},{"id":"3ac08196-8e3e-4540-a474-298506216033","cardType":"basic","points":1,"front":"For a device with useful and wasted outputs, what energy equation is used?","back":"$\\text{input energy} = \\text{useful output energy} + \\text{wasted output energy}$.","mcqOptions":[{"text":"$\\text{input energy} = \\text{useful output energy} + \\text{wasted output energy}$.","correct":true,"explanation":"Conservation of energy means all input energy must be accounted for. It is divided between useful output energy and energy wasted to the surroundings."},{"text":"$\\text{input energy} = \\text{useful output energy} - \\text{wasted output energy}$.","correct":false,"explanation":"Subtracting wasted energy fails to account for the complete input. Conservation requires the useful and wasted outputs to be added to equal the input energy."},{"text":"$\\text{useful output energy} = \\text{input energy} + \\text{wasted output energy}$.","correct":false,"explanation":"This would make useful output exceed the total input, violating conservation of energy. Input energy equals useful output energy plus wasted output energy."},{"text":"$\\text{wasted output energy} = \\text{input energy} + \\text{useful output energy}$.","correct":false,"explanation":"This incorrectly adds useful output to the input when finding wasted energy. The complete relationship is input energy equals useful output energy plus wasted output energy."}]},{"id":"777b4c6a-b741-4a93-ba33-e491874554a3","cardType":"basic","points":1,"front":"In a Sankey diagram, what does a wider arrow mean?","back":"More energy.","mcqOptions":[{"text":"More energy.","correct":true,"explanation":"In a Sankey diagram, arrow width is proportional to the amount of energy transferred. A wider arrow therefore represents more energy."},{"text":"Less energy.","correct":false,"explanation":"This reverses the meaning of arrow width. Wider arrows represent larger energy transfers, so a wider arrow means more energy, not less."},{"text":"Higher efficiency.","correct":false,"explanation":"Efficiency depends on the proportion of input transferred usefully, not on one arrow’s width alone. A wider arrow directly represents more energy."},{"text":"Greater speed.","correct":false,"explanation":"Sankey arrow widths do not show an object’s speed. They are proportional to energy transferred, so a wider arrow represents more energy."}]},{"id":"6cb4f8b8-abc3-4757-b0ba-8fc81508ffbd","cardType":"cloze","points":null,"front":"For kinetic energy, [ ], where $v$ is measured in [ ].","back":"For kinetic energy, $E_k = \\frac{1}{2}mv^2$, where $v$ is measured in m/s.","mcqOptions":[{"text":"For kinetic energy, $E_k = \\frac{1}{2}mv^2$, where $v$ is measured in m/s.","correct":true,"explanation":"Kinetic energy is half the mass multiplied by the square of speed. SI calculations require mass in kilograms and speed in metres per second."},{"text":"For kinetic energy, $E_k = mv^2$, where $v$ is measured in m/s.","correct":false,"explanation":"Omitting the factor of one-half makes every calculated kinetic energy twice as large. The correct equation is $E_k = \\frac{1}{2}mv^2$, with speed measured in m/s."},{"text":"For kinetic energy, $E_k = \\frac{1}{2}mv^2$, where $v$ is measured in km/h.","correct":false,"explanation":"Kilometres per hour cannot be inserted directly into the SI kinetic energy equation. Speed must first be converted to m/s, while $E_k = \\frac{1}{2}mv^2$."},{"text":"For kinetic energy, $E_k = \\frac{1}{2}mv$, where $v$ is measured in m/s.","correct":false,"explanation":"This misses the square on speed, confusing kinetic energy with a momentum-like expression. Kinetic energy is calculated using $E_k = \\frac{1}{2}mv^2$ and speed in m/s."}]},{"id":"69be0a31-7de0-4e6b-9ca1-15db87a1ac8c","cardType":"basic","points":1,"front":"If speed doubles and mass is unchanged, what happens to kinetic energy?","back":"It becomes four times bigger.","mcqOptions":[{"text":"It becomes four times bigger.","correct":true,"explanation":"Kinetic energy is proportional to $v^2$. Doubling speed multiplies $v^2$ by $2^2 = 4$, so the kinetic energy becomes four times bigger."},{"text":"It becomes two times bigger.","correct":false,"explanation":"This treats kinetic energy as directly proportional to speed. Because $E_k = \\frac{1}{2}mv^2$, doubling speed makes the kinetic energy four times bigger."},{"text":"It becomes eight times bigger.","correct":false,"explanation":"This incorrectly cubes the speed change. Kinetic energy depends on the square of speed, so doubling speed gives a factor of $2^2 = 4$, not eight."},{"text":"It becomes sixteen times bigger.","correct":false,"explanation":"This squares the factor twice, producing $2^4$ instead of $2^2$. With unchanged mass, doubling speed makes kinetic energy four times bigger."}]},{"id":"e4f8fbd6-9342-4613-8ad1-73626da2811c","cardType":"basic","points":2,"front":"Calculate the kinetic energy of an 80 kg cyclist and bicycle moving at 6.0 m/s.","back":"$1440\\,\\text{J}$ (or $1.4 \\times 10^3\\,\\text{J}$).","mcqOptions":[{"text":"$1440\\,\\text{J}$ (or $1.4 \\times 10^3\\,\\text{J}$).","correct":true,"explanation":"Using $E_k = \\frac{1}{2}mv^2$ gives $\\frac{1}{2} \\times 80 \\times 6.0^2 = 1440\\,\\text{J}$, which rounds to $1.4 \\times 10^3\\,\\text{J}$."},{"text":"$2880\\,\\text{J}$ (or $2.9 \\times 10^3\\,\\text{J}$).","correct":false,"explanation":"This result comes from calculating $mv^2$ and forgetting the factor of one-half. Including it gives $\\frac{1}{2} \\times 80 \\times 6.0^2 = 1440\\,\\text{J}$."},{"text":"$240\\,\\text{J}$ (or $2.4 \\times 10^2\\,\\text{J}$).","correct":false,"explanation":"This uses $\\frac{1}{2}mv$ and fails to square the speed. The correct calculation is $\\frac{1}{2} \\times 80 \\times 6.0^2 = 1440\\,\\text{J}$."},{"text":"$480\\,\\text{J}$ (or $4.8 \\times 10^2\\,\\text{J}$).","correct":false,"explanation":"This multiplies mass by speed, which resembles momentum rather than kinetic energy. Using $E_k = \\frac{1}{2}mv^2$ gives $1440\\,\\text{J}$."}]},{"id":"8c93b33e-c288-483f-a1b9-151b22bc364c","cardType":"cloze","points":null,"front":"For gravitational potential energy, [ ]; $\\Delta h$ is the [ ].","back":"For gravitational potential energy, $\\Delta E_p = mg\\Delta h$; $\\Delta h$ is the vertical height change.","mcqOptions":[{"text":"For gravitational potential energy, $\\Delta E_p = mg\\Delta h$; $\\Delta h$ is the vertical height change.","correct":true,"explanation":"The change in gravitational potential energy equals mass multiplied by gravitational field strength and vertical height change. Only the vertical change in position affects GPE."},{"text":"For gravitational potential energy, $\\Delta E_p = \\frac{1}{2}mg\\Delta h$; $\\Delta h$ is the vertical height change.","correct":false,"explanation":"The factor of one-half belongs to kinetic energy, not gravitational potential energy near Earth’s surface. The correct relationship is $\\Delta E_p = mg\\Delta h$."},{"text":"For gravitational potential energy, $\\Delta E_p = mg\\Delta h$; $\\Delta h$ is the distance travelled.","correct":false,"explanation":"Distance travelled may exceed the object’s change in height, especially along a slope. In $\\Delta E_p = mg\\Delta h$, $\\Delta h$ is the vertical height change."},{"text":"For gravitational potential energy, $\\Delta E_p = \\frac{mg}{\\Delta h}$; $\\Delta h$ is the horizontal displacement.","correct":false,"explanation":"Dividing by height gives the wrong relationship, and horizontal displacement does not determine GPE. The correct equation is $\\Delta E_p = mg\\Delta h$, using vertical height change."}]},{"id":"3c1663a9-a3b5-48dd-9c10-1d1fd018e062","cardType":"basic","points":1,"front":"Near Earth’s surface, what value of $g$ is often used if not given?","back":"$10\\,\\text{N/kg}$.","mcqOptions":[{"text":"$10\\,\\text{N/kg}$.","correct":true,"explanation":"IGCSE calculations commonly approximate Earth’s gravitational field strength as $10\\,\\text{N/kg}$ when no value is supplied, simplifying calculations while remaining close to the measured value."},{"text":"$9\\,\\text{N/kg}$.","correct":false,"explanation":"This is an inaccurate rounding of Earth’s gravitational field strength. When the question supplies no value, IGCSE calculations normally use $10\\,\\text{N/kg}$."},{"text":"$100\\,\\text{N/kg}$.","correct":false,"explanation":"This is ten times too large and may result from adding an unnecessary zero. Near Earth’s surface, the standard approximate value is $10\\,\\text{N/kg}$."},{"text":"$0.10\\,\\text{N/kg}$.","correct":false,"explanation":"This reverses the scale by treating ten as one-tenth. Near Earth’s surface, the value normally used when none is given is $10\\,\\text{N/kg}$."}]},{"id":"546a5525-f1a4-435e-8a23-9c5e80cb9e7d","cardType":"basic","points":2,"front":"A 12 kg box is lifted 1.5 m. Use $g = 10\\,\\text{N/kg}$. What is the GPE increase?","back":"$180\\,\\text{J}$.","mcqOptions":[{"text":"$180\\,\\text{J}$.","correct":true,"explanation":"The GPE increase is $mg\\Delta h = 12 \\times 10 \\times 1.5 = 180\\,\\text{J}$. Lifting the box transfers this amount of energy to its gravitational store."},{"text":"$18\\,\\text{J}$.","correct":false,"explanation":"This effectively omits the factor of $g = 10\\,\\text{N/kg}$. Multiplying all three quantities gives $12 \\times 10 \\times 1.5 = 180\\,\\text{J}$."},{"text":"$120\\,\\text{J}$.","correct":false,"explanation":"This uses $mg$ but neglects the $1.5\\,\\text{m}$ height change. The GPE increase is $12 \\times 10 \\times 1.5 = 180\\,\\text{J}$."},{"text":"$800\\,\\text{J}$.","correct":false,"explanation":"This likely divides or rearranges the given values incorrectly. GPE increase is found by multiplication: $mg\\Delta h = 12 \\times 10 \\times 1.5 = 180\\,\\text{J}$."}]},{"id":"6273a7d9-da99-4874-aa45-3b9c595fd210","cardType":"basic","points":2,"front":"For a falling object with negligible losses, what equation can link height lost to speed gained?","back":"$mg\\Delta h = \\frac{1}{2}mv^2$.","mcqOptions":[{"text":"$mg\\Delta h = \\frac{1}{2}mv^2$.","correct":true,"explanation":"With negligible losses, the decrease in gravitational potential energy equals the increase in kinetic energy. Therefore $mg\\Delta h = \\frac{1}{2}mv^2$ for an object falling from rest."},{"text":"$mg\\Delta h = mv^2$.","correct":false,"explanation":"This omits the factor of one-half from kinetic energy, causing the energy gained to be doubled. Conservation of energy gives $mg\\Delta h = \\frac{1}{2}mv^2$."},{"text":"$mg\\Delta h = \\frac{1}{2}mv$.","correct":false,"explanation":"This fails to square the speed and therefore does not represent kinetic energy. With negligible losses, the correct link is $mg\\Delta h = \\frac{1}{2}mv^2$."},{"text":"$\\frac{1}{2}mg\\Delta h = \\frac{1}{2}mv^2$.","correct":false,"explanation":"Gravitational potential energy is $mg\\Delta h$, not half this amount. Equating the full GPE loss to the kinetic energy gain gives $mg\\Delta h = \\frac{1}{2}mv^2$."}]},{"id":"20fbaf37-dd56-461d-8f47-e38bfb4c471c","cardType":"basic","points":3,"front":"A 0.50 kg ball falls 2.0 m from rest. Use $g = 10\\,\\text{N/kg}$ and ignore air resistance. What is its speed before impact?","back":"$6.3\\,\\text{m/s}$.","mcqOptions":[{"text":"$6.3\\,\\text{m/s}$.","correct":true,"explanation":"Conservation of energy gives $mg\\Delta h = \\frac{1}{2}mv^2$, so $v = \\sqrt{2g\\Delta h} = \\sqrt{40} \\approx 6.3\\,\\text{m/s}$."},{"text":"$4.5\\,\\text{m/s}$.","correct":false,"explanation":"This comes from using $v = \\sqrt{g\\Delta h}$ and omitting the factor of two. The correct calculation is $v = \\sqrt{2 \\times 10 \\times 2.0} = 6.3\\,\\text{m/s}$."},{"text":"$20\\,\\text{m/s}$.","correct":false,"explanation":"This multiplies $g$ by height as though $v = g\\Delta h$, which is dimensionally incorrect. Energy conservation gives $v = \\sqrt{2g\\Delta h} = 6.3\\,\\text{m/s}$."},{"text":"$40\\,\\text{m/s}$.","correct":false,"explanation":"This calculates $2g\\Delta h$ but forgets to take the square root. Since $v^2 = 40$, the speed is $v = \\sqrt{40} \\approx 6.3\\,\\text{m/s}$."}]}]}],"examCountdown":null,"heading":"1.7.1a Energy stores and energy transfers","title":"Energy Flashcards","topbar":{"backHref":"/igcse/physics/cie/flashcards"},"topicSidebar":"$L90"}]}],"topicId":"5408894f-a87f-577a-be14-a23ec75f9063","walled":"$L91"}],"$L92","$L93"]

1.7.1a Energy stores and energy transfers Flashcards

1.7.1a Energy stores and energy transfers Flashcards