Question

Show that in absence of any external force the velocity of centre of mass is constant

Answer 1

Answer

A. 600N

B. 2400N

Well,when the elephant is applying some amount of force in pulling the car,but still it is moving with constant velocity,that means the system is in equilibrium.What is meant by this sentence is that,there must be some opposing force of same magnitude as the applied force by the elephant,which is resulting in this equilibrium.

So,frictional force acting = force applied by the elephant in pulling it with constant velocity=600N

Now,supposing that maximum value of frictional force acting is 600N,we can say that if the elephant now exerts a force of F,then accelerationof the system will be 1.5ms−2 due to the net force (F−600)N acting forwards.

So,we can write,

Acceleration=a=1.5=F−600m=F−6001200

Or,F=600+1200×1.5=2400N