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?

The value of final velocity of the first hockey puck 2.3

Explanation:

Mass of hockey puck = m

Initial velocity

From conservation of momentum principal

4.5 m = m + m × × 3.5

= 1.5

0 = m + m × × 3.5

= - 1.75

Now final velocity of first puck

Put the values in above formula we get

2.3

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

no. dot product   =0 when vecs at right angles

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