Question

A bus of 2400 kg is moving on a straight road with a speed of 60 km/h. A car of 1600 kg is following the bus with a speed of 80 km/h. How fast is the centre of mass of the system of two vehicles moving?
(A) 70 km/h
(B) 75 km/h
(C) 72 km/h
(D) 68 km/h

Answer 1

Answer: 68km/h

Explanation:

Answer 2

Answer:

(D) 68 km/h

Explanation:

Given data from the question:

Mass of a bus, M = 2400 kg

Speed of a bus, V = 60 km/h

Mass of a car, m = 1600 kg

Speed of car, v = 80 km/h

Formula used for the velocity of the centre of mass of the system of two vehicles :

$Velocity\ of\ centre\ of\ mass=\frac{MV+mv}{M+m}$

Therefore,

$Velocity\ of\ centre\ of\ mass=\frac{2400\times 60 + 1600 \times 80}{2400+1600}$

$Velocity\ of\ centre\ of\ mass=\frac{272000}{4000}$

$Velocity\ of\ centre\ of\ mass=68$

Hence, velocity of the centre of mass of the system of two vehicles = 68 km/h.