Question

A vehicle of mass 500 kg is moving with velocity of 20m/s.Sand is dropped into it at the rate of 5kg/min.find the force needed to keep the vehicle moving with uniform velocity?

Answer 1

=>mo= initial mass = 500 kg
=>v = velocity = 20 m/s
Am = 5 kg/min = 1/12 kg/sec

=>The 500 kg is moving with
uniform speed. So there is no force
required to maintain its speed.

So in At = 1 sec. 1/12 kg of sand is added.
The momentum that is to be imparted
to 1/12 kg , so that it gains from 0
velocity to 20 m/s = Ap = 1/12 kg 20 m/s
= 20/12=5/3 kg-m/s

Force additionally required = Ap/At =
5/3 Newtons