Consider the skateboarder in the figure below. If she has a mass of 54 kg, an in
ID: 1284209 • Letter: C
Question
Consider the skateboarder in the figure below. If she has a mass of 54 kg, an initial velocity of 29 m/s, and a velocity of 11 m/s at the top of the ramp, what is the work done by friction on the skateboarder? Ignore the kinetic energy of the skateboard's wheels.
Consider the skateboarder in the figure below. If she has a mass of 54 kg, an initial velocity of 29 m/s, and a velocity of 11 m/s at the top of the ramp, what is the work done by friction on the skateboarder? Ignore the kinetic energy of the skateboard's wheels.Explanation / Answer
The difference between the enrgy at the bottom and the energy at the top will be the work performed by friction. At the bottom it is all kinetic and at the top it is kinetic plus gravitational potential.
Energy at bottom = Eb = (1/2)M*Vb^2
Energy at top = Et = (1/2)M*Vt^2 + M*g*H
Work = Eb - Et = (1/2)M*Vb^2 - [(1/2)M*Vt^2 + M*g*H]
Work = M{(1/2)[Vb^2 - Vt^2] - g*H}
M = 50 kg
Vb = 25 m/s
Vt = 7 m/s
H = 5 m
g = 9.81 m/s^2
Work = 50{(1/2){625 - 49] - 9.81*5}
Work = 50{288 - 49.05} J
Work = 11947.5 J