Question

State Newton's First and Second Laws (qualitative explanations).

Answer 1

Ans

Newton's Laws

1) If the net force(vector sum of all forces) on an object is zero, then the velocity of the object will not change at all.

Consider a block sliding with velocity v along a frictionless surface, Net force on the block is zero (weight and normal force cancel each other out as there is no motion of block in vertical direction), so block will continue to move with velocity v forever.

2) If net force(vector sum of all forces) on an object is not zero, then the acceleration of the object is given by

a = F_net / M

where M is mass of the object and F_net is the net force on the object

Now consider a ball falling freely (ignoring air resistance), there is a net force on the ball and it's the weight of the ball acting downwards. The velocity of the ball will change .The acceleration of the ball is given by a = mg/m = g

where mg = weight of the ball and m is mass