# 1. Suppose David puts a 0.50 kg rock into a sling of length 1.5 m and begins whirling the rock in a.

1. Suppose David puts a 0.50 kg rock into a

sling of length 1.5 m and begins whirling the rock in a nearly horizontal

circle, accelerating it from rest to a rate of 85 rpm after 5.0 s. What is the

torque required to achieve this feat, and where does the torque come from?

2. A 1.4 kg grindstone in the shape of a

uniform cylinder of radius 0.20m acquires a rotational rate of 1800 rev/s from

rest over a 6.0 s interval at constant angular acceleration. Calculate the

torque delivered by the motor.