Question

two bodies of masses 40kg 60kg are moving in opposite direction towards each other with velocities 40m/s and 30m/s respectively they collide and move in opposite directive if the velocity of the first body after collision in 25 m/s then what will be the velocity of the second body​

Answer 1

Given:

There are 2 bodies

For First body:

• Mass = m₁ = 40 kg
• Velocity before collision = u₁ = 40 m/s
• Final velocity after collision = v₁ = 25 m/s

For Second body:

• Mass = m₂ = 60 kg
• Velocity before collision = u₂ = -30 m/s (since it is in opposite direction)

To find:

Velocity after collision = v₂ = ?

Solution:

According to the ‘Law of conservation of Momentum’, the momentum of the object before collision should be equal to the momentum of the body after collision.

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

⇒ 40(40) + 60(-30) = 40(25) + 60(v₂)

⇒ 1600 - 1800 = 1000 + 60v₂

⇒ -200 - 1000 = 60v₂

⇒ 60v₂ = -1200

⇒ v₂ = -1200 ÷ 60

⇒ v₂ = -20

∴ Velocity of Second body = 20 m/s in opposite direction.