A car of mass 1200kg travelling at 30m/s runs into the back of a stationary lorry. The car and lorry move at 4m/s after impact. Determine the mass of the lorry.

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asked Jun 25, 2021 136k views

3 votes

A car of mass 1200kg travelling at 30m/s runs into the back of a stationary

lorry. The car and lorry move at 4m/s after impact. Determine the mass of the
lorry.

Physics
high-school

Taman Neupane asked

by Taman Neupane

4.7k points

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1 Answer

4 votes

Answer:

The mass of the lorry 7800 kg

Step-by-step explanation:

Momentum conservation law for inelastic collision:

$m1*V1 + m2*V2 =( m1 + m2)*V^(') \\ \\1200*10^(3) g * 30 m/s + m2*0 m/s =(1200*10^(3) g + m2)*4 m/s\\ \\(1200*10^(3) g * 30 m/s)/(4 m/s) -1200*10^(3) g=m2\\ \\m2=9000*10^(3) g-1200*10^(3) g=7800*10^(3) g=7800 kg$