Question

For a movie stunt, an empty truck with a mass of 2000 kg goes 10 m/s and runs into a stopped car of mass 1000 kg. the truck then keeps moving and pushes the car along with it. if there are no other forces acting on this system, describe the results of the collision?

Answer 1

Explanation:

Given that,

Mass of the truck, m₁ = 2000 kg

Mass of the stopped car, m₂ = 1000 kg

Initial speed of the truck, u₁ = 10 m/s

Initial speed of the car, u₂ = 0 (at rest)

As there is no other forces acting on this system, the momentum remains constant. Let v is the combined speed of the system after the collision. So,

$m_1u_1+m_2u_2=(m_1+m_2)v$

$2000\times 10+1000\times 0=(1000+2000)v$

v = 6.667 m/s

Therefore, the speed of the combined mass is 6.667 m/s and the speed of the combined mass is less than initial speed.  

Answer 2

ANSWER

Both trucks will move together with speed v = 6.67 m/s

so correct answer will be

The speed of the combined vehicles is less than the initial speed of the truck.

EXPLANATION

As we know that there is no external force on the system of two trucks

So here momentum of the two trucks before collision and after collision will remain same

So here we will have

$m_1v_{1i} + m_2v_{2i} = m_1v_{1f} + m_2v_{2f}$

so here we will have

$v_{1i} = 10 m/s$

$v_{2i} = 0$

$m_1 = 2000 kg$

$m_2 = 1000 kg$

now we will have

$2000\times 10 + 1000\times 0 = (2000 + 1000) v$

$v = \frac{20000}{3000} = 6.67 m/s$

so correct answer will be

The speed of the combined vehicles is less than the initial speed of the truck.