Calculating net torque

Question

A man is pushing a shopping cart, horizontally exerting a force of 200 N , 0.15 m above his hip. The weight of his upper body is 250 N located 0.1 m in front of his hip. Assuming he is moving at constant velocity in a fixed posture, what is the net joint torque about his hip?  

Answer 1

Torque = Force * distance between the point of force and point of fulcrum

 

This is the cross product between the force & distance to the fulcrum

 

Torque of force on cart about the hip = 200 N * .15m = 30 N*m

 

Torque of the weight about the hip = 250 N * 0.1m = 25 N*m

 

The difference between the torques would be the net torque of 5 N*m.