5.12 Speed and velocity
9 exam questions worth 21 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What is the unit of speed in the SI system?
Choose one answer.
Correct Not quite: the answer is m/s
Mark scheme
B: m/s
Model answer
m/s (B).
A car travels 450 m in 30 s. Calculate its average speed.
Mark scheme
v = s ÷ t = 450 ÷ 30 (1); 15 m/s (1)
Model answer
v = s / t = 450 / 30 = 15 m/s.
A runner has an average speed of 4.0 m/s. Calculate the distance she runs in 5 minutes.
Mark scheme
5 minutes = 300 s (1); s = v t = 4.0 × 300 (1); 1200 m (1)
Model answer
t = 300 s. s = v t = 4.0 × 300 = 1200 m.
Sound travels at 330 m/s in air. Lightning is seen and the thunder is heard 6.0 s later. Calculate the distance to the lightning.
Mark scheme
s = v t (1); 330 × 6.0 (1); 1980 m (1)
Model answer
s = v t = 330 × 6.0 = 1980 m (about 2 km).
A coach travels 144 km in 2.0 hours. Calculate its average speed in m/s.
Mark scheme
distance = 144 000 m (1); time = 7200 s (1); v = 144 000 ÷ 7200 (1); 20 m/s (1)
Model answer
s = 144 000 m and t = 7200 s. v = s / t = 144 000 / 7200 = 20 m/s.
A student uses a stopwatch and a ruler to measure the speed of a trolley. Give one reason why a light gate gives a more accurate measurement.
Mark scheme
a light gate measures the time automatically (1); so there is no error due to human reaction time (1)
Model answer
The light gate and data logger measure the time automatically, so there is no error from human reaction time.
A card of length 0.10 m takes 0.040 s to pass through a light gate. Calculate the speed of the trolley.
Mark scheme
v = 0.10 ÷ 0.040 (1); 2.5 m/s (1)
Model answer
v = s / t = 0.10 / 0.040 = 2.5 m/s.
Two cars each have a speed of 25 m/s. One travels north and the other south. State whether they have the same velocity and explain your answer.
Mark scheme
no / different velocities (1); velocity includes direction and they are going in opposite directions (1)
Model answer
No. Velocity has direction as well as size, and the cars are going in opposite directions.
Describe one reason why the speed of a car on a journey is not constant, and explain why a calculated speed for the whole journey is an average speed.
Mark scheme
the car speeds up and slows down / stops at traffic lights (1); total distance ÷ total time gives the mean speed over the whole journey (1)
Model answer
The car speeds up, slows down and stops during the journey. Dividing the total distance by the total time gives an average of all these speeds.
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