Question

A child on a spinning playground ride is 0.36 m from the center of the ride. The centripetal force on the child is 19 N.

What is the mass of the child if the child has a tangential speed of 0.54 m/s?

3.7 kg
13 kg
23 kg
79 kg

Answer 1

Use Fc = m v^2 / r, so m = F r / v^2.

v^2 = (0.54)^2 = 0.2916
m = (19 N)(0.36 m) / 0.2916 ≈ 6.84 / 0.2916 ≈ 23.5 kg

Closest choice: 23 kg.