Question

A meter-long ruler (meterstick) has a mass of 200 g giving it a weight of 1.96 N (nearly 1/2 pound). A pencil lying flat on a tabletop serves as a fulcrum, and if the ruler is placed with the 50-cm mark above the pencil the ruler is balanced – showing that the center of mass is at the center of the ruler.

a) Draw a diagram showing the ruler placed horizontally on the pencil with the ruler's 35- cm mark above the pencil. Draw vectors showing the two forces that act on the ruler (weight and normal force) at the INSTANT it is released (we realize, of course, that the ruler will quickly be rotationally accelerated by the net torque).
b)As you have drawn it above, is the torque acting on the pencil clockwise (CW) or counterclockwise (CCW)?
c)What is the magnitude of the torque acting on the ruler?

Answer 1

a) Image attached

b) It is acting CW

c) τ = 0.294N.m

Step-by-step explanation:

As you can see in the image, the ruler will rotate clockwise.

For the total torque: τ = -W*(0.5 - 0.35) The distance used is from 35cm to 50cm

τ = -0.294N.m The magnitude is therefore: 0.294N