An 800 kg car moving at 80 km hr−1 collides with a...
An 800 kg car moving at 80 km hr−1 collides with a 1200 kg car moving at 40 km hr−1 in the same direction. If the cars stick together, calculate their common velocity.
60 km hr−1
8 km hr−1
40 km hr−1
56 km hr−1
Correct answer is B
From momentum conservation
(800 x 80) - (1200 x 40)
= (800 + 1200) V
= 64000 - 48000 = 2000V
16000 = 2000V
V = 160002000
= 8kmh−1
The common velocity = 8kmhr−1