AQA · A-Level · Physical Education
Course version: 7582 · Version from Sept 2016
Linear motion: Weight, velocity, displacement, acceleration and momentum.
Weight is the gravitational force on a mass, calculated as W = m × g and measured in newtons (N).
Checked against the AQA 7582 specification (opens in a new tab) on .
- Point 4 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Weight is the gravitational force on a mass, calculated as W = m × g and measured in newtons (N). Velocity is the rate of change of displacement, v = s ÷ t, measured in metres per second (m s⁻¹) with direction. Displacement is the straight-line distance in a stated direction from start to finish, measured in metres (m). Acceleration is the rate of change of velocity, a = Δv ÷ t, measured in metres per second squared (m s⁻²). Momentum is the product of mass and velocity, p = m × v, measured in kilogram metres per second (kg m s⁻¹). All five are vectors, so each answer needs magnitude, unit and direction where appropriate.
For example: A 70 kg runner moving at 3 m s⁻¹ north has momentum 210 kg m s⁻¹ north.
What earns the marks
- Defines weight as the force of gravity on a mass and gives W = m × g in newtons.
- Defines velocity as rate of change of displacement and gives v = s ÷ t in m s⁻¹ with direction.
- Defines displacement as distance in a stated direction and gives the unit m.
- Defines acceleration as rate of change of velocity and gives a = Δv ÷ t in m s⁻².
- Defines momentum as mass × velocity and gives p = m × v in kg m s⁻¹.
- Classifies all five quantities as vectors and includes direction in answers.
- Applies the equations to numerical data with correct substitution and units.
Common mistakes and how to put them right
Confusing weight with mass.
Put it right: Weight is a force in newtons, while mass is a scalar in kilograms.
Treating displacement as total distance travelled.
Put it right: Displacement is the straight-line distance in a stated direction from start to finish.
Forgetting that acceleration can be negative when velocity decreases, and omitting the direction or sign.
Calculating momentum without direction.
Put it right: Momentum is a vector, so a value such as 210 kg m s⁻¹ needs a stated direction.
Exam tips
- Underline the quantity asked for in the question and match it to the correct equation and unit.
- For vector quantities, check that your answer includes a direction such as north, south, left or right.
- In multiple-choice questions, reject options that use the wrong unit, for example N for momentum or kg for weight.
Try the lesson
The start of the Linear motion: Weight, velocity, displacement, acceleration and momentum. lesson, made from checked teaching notes for this specification point.
Have a go first
A gymnast has a mass of 50 kg. Taking the acceleration due to gravity as 10 m/s², what is the gymnast's weight?
Listen
Weight is the gravitational force on a mass, calculated as W = m × g and measured in newtons (N). Velocity is the rate of change of displacement, v = s ÷ t, measured in metres per second (m s⁻¹) with direction. Displacement is the straight-line distance in a stated direction from start to finish, measured in metres (m). Acceleration is the rate of change of velocity, a = Δv ÷ t, measured in metres per second squared (m s⁻²). Momentum is the product of mass and velocity, p = m × v, measured in kilogram metres per second (kg m s⁻¹). All five are vectors, so each answer needs magnitude, unit and direction where appropriate. For example, a 70 kg runner moving at 3 m s⁻¹ north has momentum 210 kg m s⁻¹ north. A strong answer earns marks for these points. Defines weight as the force of gravity on a mass and gives W = m × g in newtons. Defines velocity as rate of change of displacement and gives v = s ÷ t in m s⁻¹ with direction. Defines displacement as distance in a stated direction and gives the unit m. Defines acceleration as rate of change of velocity and gives a = Δv ÷ t in m s⁻². Exam tip: Underline the quantity asked for in the question and match it to the correct equation and unit.
See it
Key words
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Weight
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Velocity
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Displacement
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Momentum
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See every definition
- Weight
- The gravitational force on a mass, calculated as W = m × g and measured in newtons (N).
- Velocity
- The rate of change of displacement, v = s ÷ t, measured in metres per second (m s⁻¹) with direction.
- Displacement
- The straight-line distance in a stated direction from start to finish, measured in metres (m).
- Momentum
- The product of mass and velocity, p = m × v, measured in kilogram metres per second (kg m s⁻¹).
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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