Recall typical values of speed for a person walking, running and cycling as well as the typical values of speed for different types of transportation systems.
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GCSE Physics Revision
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GCSE Physics revision
Speed
Describing motion along a line
Your specification
AQA student objectives
Learning pathway
All · Most · Some
Apply the scientific explanation of speed to a relevant example.
Analyse a new situation involving speed and explain the scientific reasoning.
Revision summary
Key knowledge
Read on screen, then print for Cornell-style active revision.
Distance vs Displacement
- Distance tells us how far an object has moved in total, regardless of direction, making it a scalar quantity.
- Displacement tells us the distance an object moves in a straight line from the start point to the finish point, and must include direction, making it a vector quantity.
- For example, a car travelling along a curved road might cover a distance of 500 m, but its displacement could be 380 m east — a shorter, straight-line value with a stated direction.
Scalar and Vector Quantities
- A scalar quantity has magnitude (size) only, with no direction — distance and speed are both scalar quantities.
- A vector quantity has both magnitude and direction — displacement is a key example of a vector quantity in motion.
The Speed Equation
- Speed tells us the distance an object travels in a given time and is calculated using the equation: v = s / t In this equation, v represents speed in metres per second (m/s), s represents distance in metres (m), and t represents time in seconds (s).
- This equation is not provided in the exam, so it must be learnt — a formula triangle can help rearrange it for distance or time.
- For example, a car travelling 260 m in 20 s has a speed of 260 / 20 = 13 text{ m/s}.
Typical Speeds to Learn
- Normal walking speed is approximately 1.5 m/s, running speed is approximately 3 m/s, and cycling speed is approximately 6 m/s.
- A car on a main road travels at around 13 m/s, a fast train in the UK at around 50 m/s, and a cruising aeroplane at around 250 m/s.
- The speed of sound in air is approximately 330 m/s, which is faster than all the transport speeds listed above.
Factors Affecting Speed
- A person's speed can vary depending on their age and fitness level, with younger, fitter individuals generally achieving faster speeds.
- Terrain affects speed — people move faster on flat ground than when travelling uphill.
- Distance also plays a role, as runners tend to be faster at the start of a long-distance run when they are less fatigued.
- The speed of sound in air is not constant — sound travels faster in warmer air than in cooler air.
Average Speed
- The speed of a moving object is rarely constant — for example, a car speeds up and slows down at different points during a journey.
- To simplify calculations, we calculate the average speed over the total length of a journey using the same equation v = s / t.
Calculating Distance from Speed
- The speed equation can be rearranged to find distance: s = v × t, where distance (m) equals speed (m/s) multiplied by time (s).
- This rearranged equation is not given in the exam and must be memorised.
- For example, a car moving at a constant speed of 12 m/s for 8 s travels a distance of 12 × 8 = 96 m.