Question 1189951

A 0.22 kg red striped pool ball is moving at 3.0 m/s North and it collides with a white cue ball that is 0.25 kg and it is moving at 1.0 m/s South. After the collision, the red striped ball continues at 2.5 m/s North.  What is the velocity of the white cue ball?

Law of conservation of momentum.
Momentum before collision = momentum after collision
Mass of ball I m1
Initial velocity u1 
Mass of ball II m2
initial velocity v2

initial momentum = m1u1+m2u2

After collision the momentum will be
m1v1 + m2v2
v1 velocity of ball I after collision
v2 velocity of ball II after collision x

0.22 * 3 + 0.25 * 1 = 0.22*2.5 + 0.25 *x

0.66 + 0.25 = 0.550 +0.25x

0.91 -0.55 = 0.25x
0.36= 0.25x

x = 1.44 m/s  ( Ball II)

Problem II similar

m1u1+m2u2 = (m1+m2) *v 
They have common velocity after they meet.












2. Two skaters are skating towards each other. The 75.0 kg man is moving at 2.0 m/s to the right, and he picks up the 40.0 kg woman skater who is moving at  -  1.5 m/s to the left.  What speed and direction do they move off together (assuming no friction on the ice)?