A0.30-kg puck, initially at rest on a frictionless horizontal surface, is struck by a 0.20-kg puck that is initially moving along the x-axis with a velocity of 9.1 m/s. after the collision, the 0.20-kg puck has a speed of 5.5 m/s at an angle of θ = 53° to the positive x-axis. (a) determine the velocity of the 0.30-kg puck after the collision, (b) find the fraction of kinetic energy lost in the collision.

a)  4.844 m/s

b) FRACTION OF LOST 1.058

Explanation:

Let 0.2 kg puck be 1 and

0.3kg puck be 2

Puck 1 is moving along x while 2 is at rest

from conservation of momentum

Along x

m1 =0.2 kg

m2 = 0.3 kg

u2 = 0

u1 = 9.1

solving for V2

Along y

Solving for Vy2

Vy2 = -2.928 m/s

Therefore,

V(final velocity of puck 2)

b) Kinetic energy lost= initial KE - Final KE

  =

= 8.281 - (3.025 +3.51)

= 8.766 J

FRACTION OF LOST  

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.