Question

A mass of 20 kg is suspended from a rope wound on a wheel of diameter 80 cm. The torque about the axis of rotation is ______.

Options

• 39.2 N m

• 78.4 N m

• 4 N m

• 2 N m

Answer 1

A mass of 20 kg is suspended from a rope wound on a wheel of diameter 80 cm. The torque about the axis of rotation is 78.4 N m.

Explanation:

`"r" ="d"/2` = 40 cm = 0.4 m,

 = `vec tau = vec"r" xx vec"F" = "rF" sin theta`

In this case, the motion of the wheel is perpendicular to the axis of rotation. Hence, e = 90°

∴ t = rF

= `0.4 xx 20 xx 9.8`

= 78.4 Nm