Adisk of radius r = 11 cm is pulled along a frictionless surface with a force of f = 16 n by a string wrapped around the edge.at the instant when d = 30 cm of string has unwound off the disk, what is the torque exerted about the center of the disk?

1.76 Nm

Explanation:

If the force pulls horizontally, this means that the force is tangent to the disk at any point of the string unwinding process, so the distance d is irrelevant.

In this case, the torque is directly given by the product of the force times the distance perpendicular to the center of the disk, which is just the radius, as follows:

τ = F * r = 16 N. (0.11) m = 1.76 Nm

0.4 A

Explanation:

From the question,

Electric power = Voltage×current

P = VI Equation 1

Make I the subject of the equation

I = P/V Equation 2

Given: P = 96 J/s, V = 230 V.

Substitute into equation 2

I = 96/230

I = 0.4 A.

Hence the current is 0.4 A