A body of mass 12kg traveling at 4.2ms‾¹ collides with a second body of mass 18kg at rest. Calculate their common velocity if the two bodies coalesce after collision

A. 1.5 ms‾¹
B. 1.4 ms‾¹
C. 2.1 ms‾¹
D. 1.7 ms‾¹

Correct Answer:

Option D = 1.7 ms‾¹

Explanation

Sum of momentum before the collision
M1U1 + M2U2
12 x 4.2 + 18 x 0
12 x 4.2
= 50.4
Sum of momentum after collision
(m1 + m2)v
= (12 + 18)v
= 30v
V = 50.4/30
= 1.7ms‾¹