Question

A magnetic hockey puck (0.40 kg) hits another hockey puck (0.40 kg) at rest and both travel together to the right at 8.0 m/s. How fast was the first hockey puck initially moving?
m/s

Answer 1

Answer

= 16 m/s

Explanation

The law conservation of energy states that, momentum before collision is equal to momentum after collision.

m₁v₁ = m₂v₂

momentum before collision = (0.40 × v) + (0.40 × 0)

= 0.4v Km/s

momentum after collision = (0.40+0.40) × 8.0

= 0.8 ×8.0

= 6.4 Km/s

m₁v₁ = m₂v₂

0.4v Km/s = 6.4 Km/s

v = 6.4/0.4

= 16 m/s

Answer 2

This problem can be solved through the Inelastic Collision Formula:
mass1 x in.velocity1 + mass2 x in.velocity2 = mass1+mass2 (final velocity)

Substituting the values, we have:
0.40 kg x in.velocity1 + 0.40 kg x 0 m/s = 0.80 kg (8.0m/s)

Solving for the unknown initial velocity of the moving hockey puck we have:
in.velocity1 = (6.4 kgm/s - 0) / 0.40 kg
= 16 m/s