Arailroad car moves under a grain elevator at a constant speed of 3.20 m/s. grain drops into the car at the rate of 240 kg/min. what is the magnitude of the force needed to keep the car moving constant speed if friction is negligible?

F = 768 N                  

Explanation:

It is given that,

Speed of the elevator, v = 3.2 m/s

Grain drops into the car at the rate of 240 kg/min,

We need to find the magnitude of force needed to keep the car moving constant speed. The relation between the momentum and the force is given by :

Since, the speed is constant,

F = 768 N

So, the magnitude of force need to keep the car is 768 N. Hence, this is the required solution.