What is the Kinetic and Internal Energy of a Car-Truck Collision?

[gmagnus]

Homework Statement

A 1200 kg car moving at 88 km/h collides with a 7600 kg truck moving in the same direction at 65 km/h. The two stick together, continuing in their original direction at 68 km/h. Determine the kinetic energy of the center of mass of the (car + truck) system. Determine the internal energy of the (car + truck) system before the collision. Determine the internal energy of the (car + truck) system after the collision.

Homework Equations

m₁v₁ + m₂v₂ = (m₁ + m₂)v_f

Kinetic energy of a system is K = K_cm + K_int

K = 1/2mv²

The Attempt at a Solution

88 km/h converted to 24.4444 m/s
65 km/h converted to 18.0556 m/s

 

[rock.freak667]

You'd need to find the velocity of the (car+truck) system after collision to get the kinetic energy.