Some units are derived from other units by using an equation.
Pressure is calculated using the equation
pressure=force÷area\text{pressure} = \text{force} \div \text{area}pressure=force÷area
Show that the unit of pressure can be written as N/m2\text{N/m}^{2}N/m2.
Give the name of the unit that is equal to 1 N/m2.
Give the SI unit of density.
Efficiency is calculated using the equation
efficiency=useful energy transferred÷total energy supplied\text{efficiency} = \text{useful energy transferred} \div \text{total energy supplied}efficiency=useful energy transferred÷total energy supplied
Explain why efficiency has no unit.
A student says that the unit of acceleration is m/s\text{m/s}m/s because
acceleration=change in velocity÷time taken\text{acceleration} = \text{change in velocity} \div \text{time taken}acceleration=change in velocity÷time taken
Explain why the student is wrong.
39 exam-style questions on Edexcel GCSE Physics 1.1 Units and quantities, covering 1.1.1 SI units for physical quantities and 1.1.2 Unit prefixes, conversions, significant figures and standard form. Each one has a worked solution and a mark scheme showing where the marks go.