Question

A wheel of a cart makes 2 revolutions per second. If the

diameter is 84 cm, find the speed in km/h
​

Answer 1

19.0km/h (rounded to 3 s.f.)

Explanation:

To find the speed, we need to find the distance travelled per second before finding the distance per hour (speed).

1 revolution =
`\pi` × 84

= 84
`\pi` cm

= 0.00084
`\pi` km

2 revolutions = 0.00084
`\pi` km × 2

= 0.00168
`\pi` km

1 second --- 0.00168
`\pi` km

1 minute --- 0.00168
`\pi` km × 60 = 0.1008
`\pi` km

1 hour --- 0.1008
`\pi` km × 60 = 6.048
`\pi` km

= 19.0 km (rounded to 3 s.f.)