The average speed of an object is the distance it travels each second (m/s). It is a scalar quantity.

The instantaneous speed of an object is the speed at a particular moment.

Some quantities only have magnitude (size), and not direction. This includes distance and speed.

A scalar quantity only has magnitude (size).

The relative speed of objects is the difference in their speeds taking into account direction of movement.

Different speeds (v=x/t)

Combined science

In the Energy of moving objects unit, they will build on this knowledge to learn how to calculate the amount of energy of objects have because they are moving, stretched or in a gravitational field; and to calculate energy transfers using knowledge of energy conservation and dissipation.

In the Moving by force unit, pupils learnt how to calculate speed and describe motion using distance-time graphs, apply Newton’s First Law of motion and calculate the amount of energy needed to move an object to a new position.

This unit covers vector-scalar distinctions in displacement, distance, velocity, and speed. It explores speeds, acceleration, motion graphs, and formulas for uniform and non-uniform motion. It also includes understanding circular motion and conducting accurate measurements, and calculations.

Measuring and calculating motion

A dynamics trolley is a wheeled object used in experiments. It moves very smoothly over flat surfaces.

The average speed is the total distance travelled divided by the total time for a journey.

The instantaneous speed of an object is the speed at a particular moment in time.

An anomalous reading is a result which is significantly outside the pattern in a set of results.

Measuring instantaneous speed practical (v=x/t)

A measurement is repeatable if the same (or similar) results are obtained when the same person repeats the investigation using the same method.

A measurement is reproducible if the same (or similar) results are obtained when the same person repeats it using a different method, or a different person repeats it using the same method.

The instantaneous speed of an object is its speed at a particular moment in time.

If two variables are directly proportional, when one variable increases, the other increases at the same rate.

Measuring instantaneous speed analysis (v=x/t)

A speed camera is used to measure speed of vehicles on roads. It captures images of any vehicle exceeding the speed limit of the road.

A radar gun uses shifts in the frequency of reflected radio waves to measure the speed of objects.

A light gate can be used to measure speed. It uses an infrared beam to turn a timer on and off as an object passes through.

Automated measurement of speed

The displacement of an object is the distance travelled in a particular direction from a starting point.

A vector is a quantity with magnitude (size) and direction. Displacement and velocity are both vector quantities.

The velocity of an object is its speed in a particular direction.

Displacement and velocity as vectors (v=x/t)

The displacement of an object is the distance and direction from a specific point. Displacement is a vector.

A displacement-time graph shows the displacement of an object over a period of time.

A motion sensor measures the distance between itself and an object. We can use the measurements to calculate and plot graphs of displacement, velocity and acceleration.

Velocity on a graph (v = x ÷ t)

A displacement-time graph shows the change in displacement over a time period. The displacement along a straight line can be positive or negative.

The gradient on a displacement-time graph gives the instantaneous velocity.

The instantaneous velocity is the velocity of an object at a particular moment in time.

Calculating from displacement-time graphs (v=x/t)

The acceleration of an object is the rate of change of velocity. This is how much the velocity changes per second.

Deceleration is used to describe a change in velocity where the object slows down.

The velocity of an object is the speed in a particular direction. This is the rate of change of displacement.

A rate of change is how much a quantity is changing by every second.

Acceleration (a=(v-u)/t)

The acceleration of an object is the change in velocity per second.

The velocity of an object is the change in displacement per second.

Measuring acceleration practical (v=x/t, a=(v-u)/t)

A ramp with a slope to counteract the effect of friction.

The final velocity of an object is the velocity it finishes with after a phase of motion.

A light gate can be used to measure velocity. It uses an infrared beam to turn a timer on and off as an object passes through.

Measurements are repeatable if they are very similar when the same procedure is carried out by the same person or team.

When the acceleration is constant, it is described as uniform acceleration.

Measuring acceleration analysis (v = x ÷ t, a = (v – u) ÷ t)

A velocity-time graph shows the velocity of an object over a period of time.

Calculating from velocity-time graphs (a=(v-u)/t)

A displacement–time graph shows the displacement of an object over a period of time.

A velocity–time graph shows the velocity of an object over a period of time.

The velocity of an object is the rate of change of displacement. This is how fast it is moving in a particular direction.

Calculating from motion graphs (a=(v–u)/t  and v=x/t)

The initial velocity of an object is the velocity it starts with during a phase of motion.

The average velocity of an object travelling in a straight line is the change in distance divided by the time taken.

The average acceleration of an object is the change in velocity divided by the time taken.

Measuring and calculating motion

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These lessons will be removed by end of Summer Term 2025.