Question

an automobile of mass 1500 kg moving at 25 meters per second collides with a truck of mass 4500 kg at rest. the car and the truck bounce off each other completely elastically. what is the final velocity of the truck after the Collision call the direction of the automobile before the Collision positive

Answer 1

here,

mass of car , m1 = 1500 kg

mass of truck , m2 = 4500 kg

speed of car , u1 = 25 m/s

let the final speed of car be v1 and truck be v2

using conservation of momentum

m1 * u1 = m1 * v1 + m2 * v2

1500 * 25 = 1500 * v1 + 4500 * v2 .....(1)

and

using conservation of energy

0.5 * m1 * u1^2 = 0.5 * m1 * v1^2 + 0.5 * m2 * v2^2

1500 * 25^2 = 1500 * v1^2 + 4500 * v2^2 .....(2)

from (1) and (2)

v1 = -12.5 m/s

v2 = 12.5 m/s

the final speed of truck after the collison is 12.5 m/s