Question

Alice and Bob lift a table, on which Carl is sitting. The table is 2 m long, weighs 150 N, is uniform and stays horizontal. Carl weighs 700 N and is sitting 0.60 m from Alice. Determine the force exerted by Alice.

Answer 1

it is given that, Carl's weight = 700N and weight of the table = 150N

so, sum of weight of the table and Carl = 150N + 700N = 850N , this should be equal sum of weight of Alice and Bob. This is based on torque concept. To left, the table , Alice and Bob must be at opposite ends of the table.

if we assume Alice is at the left end of the table , then weight of Carl and table produces clockwise torque. the upward force that Bob exerts will counter clockwise torque.

in mathematical,

clockwise torque = 700 × 0.6 + 150 × 1

= 420 + 150 = 570N

counterclockwise torque = F × 2 , here F is the force exerted by Bob on the table.

at equilibrium, F × 2 = 570

F = 285N ,

now, F' + 285 = 850 , here F is the force exerted by Alice on the table.

F' = 565N