Question

Consider the collision between two hockey pucks in the figure below. They do not stick together. Their speeds before the collision are v1i = 28 m/s and v2i = 13 m/s. It is found that after the collision one of the pucks is moving along x with a speed of 2 m/s. What is the final velocity of the other puck?

Answer 1

let m is the mass of hockey puck.

Apply conservation of momentum in x-direction

m*v1ix + m*v2ix = m*v1fx + m*v2fx

v1ix + v2ix = v1fx + v2fx

28*cos(30) + 0 = v1fx + 2

v1fx = 24.25 - 2

= 22.25 m/s

Apply conservation of momentum in x-direction

m*v1iy + m*v2iy = m*v1fy + m*v2fy

v1iy + v2iy = v1fy + v2fy

-28*sin(30) + 13 = v1fy + 0

v1fy = -14 + 13

= -1 m/s

so, v1f = sqrt(22.25^2 + 1^2)

= 22.8 m/s <<<<<<<<<<<<<<<<<<----------Answer

theta = tan^-1(v1fy/v1fx)

= tan^-1(-1/22.25)

= 2.57 degrees below +x axis

= 357.43 counterclockwsie from +x axis <<<<<<<<<<<<<<<<<<----------Answer