A car with a mass of 800 g and velocity of 15 m/s collided with a truck of a velocity of 20 m/s, if the momentum is conserved what is the mass of the truck?

Question: A car with a mass of 800 g and velocity of 15 m/s collided with a truck moving in opposite direction with a velocity of 20 m/s, if the momentum is conserved and they both move with a common velocity of 10 m/s, what is the mass of the truck?

0.133 kg

Explanation:

Applying the law of conservation of momentum,

Total momentum before collision = Total momentum after collision

mu+m'u' = V(m+m') Equation 1

Where m = mass of the car, m' = mass of the truck, u = initial velocity of the car, u' = initial velocity of the truck, V = common velocity.

From the question,

Given: m = 800 g = 0.8 kg, u = 15 m/s, u' = -20 m/s, V = 10 m/s

Substitute these values into equation 2

(0.8*15)+(m'*20) = 10(0.8+m')

Solve for m'

12-20m' = 8+10m'

-20m'-10m' = 8-12

-30m' = -4

m' = -4/-30

m' = 0.133 kg