f-5905-4196-8341-3396f41ef0f8","topicSlug":"a-level-mechanics-3-projectiles","cards":[{"id":"1262bbe9-047d-4873-9768-755afb453320","cardType":"basic","front":"List 2 physical factors ignored in the standard particle model of a projectile.","back":"

Air resistance
Dimensions of the object

","points":2,"mcqOptions":[{"text":"

Air resistance
Dimensions of the object

","correct":true,"explanation":"The standard particle model treats the projectile as a point mass and neglects air resistance, so these two physical factors are ignored."},{"text":"

Gravity
Mass of the object

","correct":false,"explanation":"Gravity is included as the projectile’s constant downward acceleration, while mass is not usually needed once the forces are modelled. The ignored factors are air resistance and the object’s dimensions."},{"text":"

Initial speed
Launch angle

","correct":false,"explanation":"Initial speed and launch angle are essential starting conditions for the motion, not assumptions omitted by the model. The model ignores air resistance and the dimensions of the object."},{"text":"

Horizontal velocity
Vertical velocity

","correct":false,"explanation":"The velocity components describe the projectile’s motion and are used in the equations. The particle model instead ignores air resistance and the physical dimensions of the object."}]},{"id":"8aa47a49-6d3d-4d8b-bf43-ea68035096d8","cardType":"basic","front":"Why is the horizontal acceleration of a projectile modeled as zero?","back":"There are no horizontal forces acting on the particle after launch.","points":2,"mcqOptions":[{"text":"There are no horizontal forces acting on the particle after launch.","correct":true,"explanation":"With no horizontal force after launch, Newton’s second law gives zero horizontal acceleration, so the horizontal velocity remains constant throughout the flight."},{"text":"There are no vertical forces acting on the particle after launch.","correct":false,"explanation":"Gravity is a vertical force and causes the projectile’s downward acceleration. The horizontal acceleration is zero because there are no horizontal forces acting after launch."},{"text":"The particle has no velocity acting on it after launch.","correct":false,"explanation":"A projectile continues moving with its initial velocity components after launch. Its horizontal acceleration is zero specifically because no horizontal force acts, not because its velocity disappears."},{"text":"The particle has constant vertical velocity after launch.","correct":false,"explanation":"The vertical velocity changes because gravity produces constant downward acceleration. The horizontal velocity is constant because no horizontal force acts on the particle."}]},{"id":"15dd8dbf-9788-4f48-8ab4-013a7b5d54ae","cardType":"basic","front":"A particle is launched with speed $U$ at angle $\theta$ to the horizontal. What is its initial vertical velocity component $u_y$?","back":"$$U\u0010\nsin\\theta$","points":1,"mcqOptions":[{"text":"$$U\u0010\nsin\\theta$","correct":true,"explanation":"Resolving the initial velocity vector vertically gives the opposite component in the right-angled triangle, so the initial vertical velocity is $U\\sin\\theta$."},{"text":"$$U\ncos\\theta$","correct":false,"explanation":"Using cosine gives the component adjacent to the launch angle, which is horizontal. The vertical component is opposite the angle and therefore uses sine: $U\\sin\\theta$."},{"text":"$$\\frac{U}{\\sin\\theta}$","correct":false,"explanation":"Dividing by sine is not the rule for resolving this velocity vector and gives the wrong dependence on the angle. The vertical component is found by multiplying $U$ by $\\sin\\theta$."},{"text":"$

Projectiles Flashcards

Projectiles Flashcards