Question

A hockey puck of mass m traveling along the x axis at 4.5 m/s hits another identical hockey puck at rest. If after the collision the second puck travels at a speed of 3.5 m/s at an angle of 30° above the x axis, what is the final velocity of the first puck?

Answer 1

Answer:

The value of final velocity of the first hockey puck $v_{1} _{f} =$ 2.3 $\frac{m}{s}$

Explanation:

Mass of hockey puck = m

Initial velocity $v_{1}_{i} = 4.5 \frac{m}{s}$

From conservation of momentum principal

4.5 m = m $v_{1x} _{f}$ + m × $\cos 30$ × 3.5

$v_{1x} _{f}$ = 1.5 $\frac{m}{s}$

0 = m $v_{1y} _{f}$ + m × $\sin 30$ × 3.5

$v_{1y} _{f}$ = - 1.75 $\frac{m}{s}$

Now final velocity of first puck

$v_{1} _{f} = \sqrt{v_{1x} _{f}^{2} + {v_{1y} _{f}^{2} }$

Put the values in above formula we get

$v_{1} _{f} = \sqrt{(1.5)^{2} + (-1.75)^{2} }$

$v_{1} _{f} =$ 2.3 $\frac{m}{s}$

This is the value of final velocity of the first hockey puck.