Automated measurement of speed | Starter Quiz | Oak National Academy

Speed is a scalar quantity. Which of the following describes a scalar quantity?

• It is a quantity that has magnitude (size) and direction.

• It is a quantity that has only magnitude (size) and not direction.

• It is a quantity that has only direction and not magnitude (size).

• It is a quantity that has no direction and no magnitude (size).

Answer explanation

Scalar quantities like speed have only magnitude (size) and not direction.

Match the the following objects with the example speeds.

• person walking

• 330 m/s

• sound wave in air

• 10 cm/minute

• snail moving across floor

• 70 mph

• space station orbiting Earth

• 1.5 m/s

• car on a motorway

• 7.7 km/s

Answer explanation

Speed can be measured in a range of units including mph (miles per hour), m/s (metres per second), km/s (kilometres per second) and a few more unusual ones.

A dog runs 80 m in 20 seconds. Which of the following calculations would give the speed of the dog?

A hot air balloon flies at a speed of 15 km/h for 5 hours. Which of the folloiwing is the distance it travels?

• 3 km

• 10 km

• 20 km

• 75 km

• 150 km

Answer explanation

distance = speed × time = 15 km/h × 5 h = 75 km

A sound waves takes 30 s to travel 45 000 m through water. Which of the following gives the speed of sound in water?

• 330 m/s

• 1350 m/s

• 1500 m/s

• 15 000 m/s

• 1 350 000 m/s

Answer explanation

speed = distance ÷ time = 45 000 m ÷ 30 s = 1500 m/s

A dynamics trolley is rolled down a ramp reaching a speed of 2.4 m/s. Calculate the time it will take for the trolley to pass between a pair of markers which are 20 cm apart.

Answer explanation

time = distance ÷ speed = 0.20 ÷ 2.5 = 0.08 s