Question

A ball is allowed to roll down from an inclined plane.it reaches the foot of the plane and continue to roll on the ground.it stops after travelling some distance.is this violation of law of inertia?give reason

Answer 1

The law of inertia simply states that an object continues to be in a state of rest or of uniform motion along a straight line until it is compelled to change its state by an external force. 

This property of every body is known as inertia- the property by the virtue of which a body maintains its state (rest/motion) until affected by an (external) force. 

Now, a ball rolling down an inclined plane is in a state of motion, and it should maintain its state of motion, according to the law of inertia, but only until it is not acted upon by an external force. 

Enter the force of friction, which is present on both the plane and the ground. This is an external force, which would compel the ball to eventually come to a halt. So, you see, inertia cannot be maintained as there is a net force acting upon the body. 

Answer 2

Answer: Now, a ball rolling down an inclined plane is in a state of motion, and it should maintain its state of motion, according to the law of inertia, but only until it is not acted upon by an external force. Enter the force of friction, which is present on both the plane and the ground.