A student on a skateboard is moving at a speed of 1.40 m/s at the start of a 2.45 m high and 12.4 m long incline. The total mass is 45.0 kg, air resistance and rolling resistance can be modeled as a constant friction force of 41.0 N, and the speed at the lower end of the incline is 6.60 m/s. Determine the work done (in J) by the student as the skateboard travels down the incline. J

   W = 936 J

Explanation:

Let's analyze this problem we must use energy conservation, but there is a friction force that creates a working device that must be equal to the variation of mechanical energy between the starting and ending points.

The energy work theorem states that work is equal to the variation of the kinetic energy of the body,

           W = - K_{o}

           W = ½ m v² - ½ m v₀²

           W = ½ m (v² -v₀²)

let's calculate

           W = ½ 45 (6.6² -1.4²)

           W = 936 J

This is the work done by the student

a sonic boom is a loud boom that breaks the sound barrier

explanation: