Question

Consider an inelastic collision between two spheres of different masses, m1= 1kg and m2=3 kg, in the +x direction. Ball M1 is moving at speed, v1=3.0ms, and ball 2 is moving towards ball 1 at speed, v2=1 kg.

1. What will happen to the velocities of the two balls after a completely inelastic collision? Explain your reasoning. Do NOT do any calculation yet. Use your physical intuition and what know so far about collisions.

2. Which physical principles were used to find velocities of balls? Calculate the final velocities of the balls after the collsion.

3. What is the change in internal energy?

Answer 1

1. A perfectly inelastic Collison there is maximum loss in kinetic energy, which in one dimensional head on collision corresponds to the object after colliding sticks together and move as a single object. So after the collision both ball will move with same velocity.

2. We will use principle of conservation of momentum to find out the final velocity. Suppose the final velocity is v. Then final momentum = (m1+me). v

Initial momentum = m1.V1 + m2.​​​​V2

So in +X direction, initial momentum is

Pi = (1.3 -3. 1 ) kg m/sec =0

Pf = Pi= 0

So the final velocity of the combined object is zero.

3.

Change in internal energy = loss in kinetic energy = K.E(initial) - K.E(final) = K.E(initial) - 0 = 6 J