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Class 9
Science
Force and Laws of Motion
an object of mass 1 kg travelling in a straight li...

Question:
An object of mass 1 kg travelling in a straight line with a velocity of 10 m s^-1 collides with, and sticks to, a stationary wooden block of mass 5 kg. Then they both move off together in the same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.

Answer:

Mass of the object, m1 = 1 kg

Mass of the wooden block, m2 = 5 kg

Velocity of the object before collision, v1 = 10 m/s

Velocity of the wooden block before collision, v2 = 0 m/s

Total mass of the combined system = m1 + m2 = 1 + 5 = 6 kg

∴ Total momentum before collision = m1 v1 + m2 v2

= 1 (10) + 5 (0) = 10 kg m s⁻¹

Velocity of the combined object = v

Momentum = total mass x velocity of combined object

= (m₁ + m₂) v = 6v

According to the law of conservation of momentum:

Total momentum before collision = Total momentum after collision

m₁ v₁ + m₂ v₂ = (m₁ + m₂) v

10 = 6 v

The total momentum after collision is also 10 kg m/s.

Hence, velocity of the combined object after collision =

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