Question

A body of mass 80 kg with a velocity of 6 m/s hits a stationary body of mass 40 kg. If the bodies move together after the impact, calculate the velocity of the composite body just after the impact. 3 points
4. 5 m/s
4. 0 m/s
4. 1 m/s
18. If the bodies do not move together and the body of mass 40 kg is moving at 3 m/s in the same direction as the body of mass 80 kg, what is the velocity of the 80 kg mass after impact. 5. 0 m/s
5. 1 m/s
5. 10 m/s

Answer 1

Answer:

1.

Use momentum conservation

$80 \times 6 + 40 \times 0 = 120 \times v \\ \\ v = \frac{480}{120} = 4 \: m {s}^{ - 1}$

2.

Again same concept

$80 \times 6 = 40 \times 3 + 80v \\ \\ 80v = 480 - 120 = 360 \\ \\ v = \frac{360}{80} =4.5 \: m {s}^{ - 1}$