Question

A 1200 kg car is traveling 21.1 m/s. It collides with a stationary car of mass 1500 kg, and the two vehicles lock together. What is the speed of the combined cars immediately after the collision?

A) 7.5 m/s

B) 16.5 m/s

C) 9.4 m/s

D) 11.8 m/s

Answer 1

C) 9.4 m/s

Step-by-step explanation:

`m_1` = Mass of moving car = 1200 kg

`u_1` = Initial velocity of moving car = 21.1 m/s

`m_2` = Mass of stationary car = 1500 kg

`u_2` = Initial velocity of stationary car = 0

v = Velocity of the combined cars

As the momentum in the system is conserved we have

`m_1u_1+m_2u_2=(m_1+m_2)v\\\Rightarrow v=(m_1u_1+m_2u_2)/(m_1+m_2)\\\Rightarrow v=(1200* 21.1+1500*0)/(1200+1500)\\\Rightarrow v=9.378\approx 9.4\ \text{m/s}`

The velocity of the combined mass is 9.4 m/s.