Question

The two objects A and B above are balanced. The mass of object A is 2.2 kg. the mass of object B is 1kg. The rigid bar connecting A and B has no significant mass. It's supported by a fulcrum (without friction). The lengths of the lever arms are L1= 1.2m and L2=2.64m.

a) Calculate the weight F1 of object A

b) Calculate the weight F2 of object B

c) Calculate the torque of F1 around the fulcrum

d) Calculate the torque of F2 around the fulcrum

e) Is the bar in rotational equilibrium? Answer this by stating the net torque

f) How far away is the center of mass of objects A and B from the fulcrum?

Answer 1

a) Weight of object A = 2.2*9.8 = 21.56 Kg

b) Weight of object B = 1*9.8 = 9.8 Kg

For calculating torque i'm taking counter clockwise direction as positive.

c) The torque of F1 around the fulcrum = 21.56*1.2 = 25.872 Nm

d) The torque of F2 around the fulcrum = 9.8*2.64 = -25.872 Nm

e) Net torque = 25.872 - 25.872 = 0. Therefore the bar is in rotational equilibrium

f) Center of mass of A and B from fulcrum =

Therefore the center of mass of A and B is on the fulcrum.