Question

A car of mass 1000 kg travelling at 32 m/s clashes into a rear of a truck of mass 8000 kg moving in the same direction with a velocity of 4 m/s. After the collision the car bounces with a velocity of 8 ms^–1. The velocity of truck after the impact is _______ m/s 

(A) 8 

(B) 4 

(C) 6 

(D) 9

Answer 1

Correct option: (D) 9

Explanation:

m₁ = 1000 kg

v₁ = 32 m/s

m₂ = 8000 kg

v₂ = 4 m/s.

after collision, v₁¹ = – 8 m/s

v₂¹ = 2

momentum is conserved hence

m₁v₁ + m₂ v₂ = m₁ v₁¹ + m₂ v₂¹ 

(1000 × 32) + (8000 × 4) = (1000 × – 8) + (8000 v₂¹)

∴ 32000 + 32000 = – 8000 + 8000 v₂¹ 

∴ 64000 = 8000 (v₂¹ – 1)

∴ v₂¹ – 1 = 8

v₂¹ = 9 m/s