Posted by **Katie** on Saturday, March 3, 2012 at 12:14pm.

In a game of pool, the cue ball strikes another ball initially at rest. After the collision, the cue ball moves at 4.15 m/s along a line making an angle of -25° (i.e. below the x-axis) with its original direction of motion (the x-axis), and the second ball has a speed of 2.846 m/s.

Find the angle between the direction of motion of the second ball and the original direction of motion of the cue ball. Assume the masses are equal.

Find the original speed of the cue ball.

Is kinetic energy conserved?

- physics -
**Elena**, Saturday, March 3, 2012 at 5:17pm
According to the law of conservation of linear momentum

vector(p)= vector(p1)+ vector(p2),

Let vector( p) is directed along +x-axis. Then vector (p1) is

below x-axis and vector(p2) is above it.

Projections on axes are

x: v = v1•cosα +v2•cosβ

y: 0 = - v1•sin α +v2•sinβ

sinβ = v1•sin α/v2 = 0.616.

β = arcsin 0.616 = 38 degr.

cos β = 0.788.

v = 4.15•0.906+2.846•0.788=6 m/s.

At elastic collision the kinetic energy is conserved.

## Answer this Question

## Related Questions

physics - In a game of pool, the cue ball strikes another ball of the same mass ...

physics - In a game of pool the cue ball strikes another ball of the same mass ...

physics - In a game of pool the cue ball strikes another ball of the same mass ...

Impulse and Momentum - In the game of billiards, all the balls have ...

physics - A cue ball initially moving at 2.6 m/s strikes a stationary eight ball...

Physics - In a game of pool the cue ball strikes another ball of the same mass ...

college physics - A cue ball initially moving at 4.3m/s strikes a stationary ...

Physics - In a game of pool the cue ball strikes another ball of the same mass ...

Physics HELP HELP - A cue ball traveling at 4.0 m/s makes a glancing, elastic ...

Physics - A cue ball traveling at 4.0 m/s makes a glancing, elastic collision ...