Question

Before cutting the spring, the 800 kg car moves to the right with a speed of 12 m/s.  After cutting the spring, determine the speed and momentum of the 900 kg car.

Answer 1

Given data:

* The mass of the car before cutting the spring is m_1 = 800 kg.

* The speed of the car before cutting the spring is u = 12 m/s.

* The mass of the car after cutting the spring is m_2 = 900 kg.

Solution:

According to the law of conservation of momentum, the momentum of the car remain conserved before and after cutting the spring,

`m_1u=m_2v`

where v is the final velocity of the car after cutting the spring,

Substituting the known values,

`\begin{gathered} 800*12=900* v \\ v=(800*12)/(900) \\ v=(9600)/(900) \\ v=10.66667\text{ m/s} \end{gathered}`

Thus, the speed of a 900 kg car is approximately 10.67 m/s.

The momentum of 900 kg car is,

`\begin{gathered} p=m_2v \\ p=900*10.66667 \\ p\approx9600\text{ kgm/s} \end{gathered}`

Thus, the momentum of the 900 kg car is 9600 kgm/s.