Different speeds (v=s/t) | Exit Quiz | Oak National Academy

Match the key words or phrases to their definitions.

• magnitude

• the size of a quantity

• relative speed

• the speed of one object compared to the speed of another object

• scalar

• a quantity that has only magnitude (not direction)

• average speed

• the speed of an object at a particular moment of time

• instantaneous speed

• the average distance travelled every second

Answer explanation

The average distance travelled every second is average speed while the speed at a particular moment is instantaneous speed. Scalar quantities have only magnitude (size) and no direction. Relative speed is a comparison of the speeds of two objects.

Match the activity to the typical speed for that activity.

• running

• 0.5 m/s

• cycling

• 1.5 m/s

• swiming

• 6 m/s

• walking

• 3 m/s

Answer explanation

The typical speeds for these activities are: swimming 0.5 m/s, walking 1.5 m/s, running 3 m/s and cycling 6 m/s. Remember that these are typical values, not record-breaking values, which would be much higher.

A skateboarder travels a distance of 400 m in 50 s. What is their average speed?

• 350 m/s

• 20 000 m/s

• 450 m/s

• 8 m/s

• 0.125 m/s

Answer explanation

v = s ÷ t = 400 m ÷ 50 s = 8 m/s

Sound waves travel at 330 m/s in air. A boy sees a firework explode in the distance. The sound arrives 6.0 s after the flash. How far away from the boy did the firework explode (to 2 s.f.)?

• 55 m

• 2.0 km

• 1.0 km

• 200 m

Answer explanation

v = s ÷ t, so s = v × t = 330 m/s × 6.0 s = 1980 m = 2 km (to 2 significant figures)

Two cars are traveling in opposite directions (towards each other). The first car is travelling at 30 km/h and the second is travelling at 70 km/h. What is the relative speed of the cars?

• 30 km/h

• 70 km/h

• 40 km/h

• 100 km/h

• 2100 km/h

Answer explanation

The relative speed is 30 km/h + 70 km/h = 100 km/h.

During a race, cyclist A is traveling at 10 m/s and is 200 m behind cyclist B, who is travelling at 8 m/s in the same direction. How long will it take cyclist A to catch up with cyclist B?

• 20 s

• 25 s

• 160 s

• 250 s

• 100 s

Answer explanation

The relative speed is 2 m/s (10 – 8). The time is found using t = s ÷ v = 200 m ÷ 2 m/s = 100 s.