Problem #3

Gravitational Potential

A 10.0 kg microwave oven is pushed 8.00 m up the sloping surface of a loading ramp inclined at an angle of 36.9 degrees above the horizontal, by a constant force F with a magnitude 110 N and acting parallel to the ramp. The coefficient of kinetic friction between the oven and the ramp is 0.250. (a) What is the work done on the oven by the force F? (b) What is the work done on the oven by the friction force? (c) Compute the increase in potential energy for the oven. (d) Use your answers to parts (a), (b), and (c) to calculate the increase on the oven's kinetic energy. (e) Use F=ma to calculate the acceleration of the oven. Assuming that the oven is initially at rest, use the acceleration to calculate the oven's speed after traveling 8.00 m. From this, compute the increase in the oven's kinetic energy, and compare it to the answer you got in part (d).




Be sure that you think of each force separately and how each component of the gravitational force effects the others; set your coordinate system tilted 36.9 degrees for dealing with the incline so that the gravitational force isn't along the y-axis. And above all, have fun!!





Answer
(a) 880 J
(b) -157 J
(c) 471 J
(d) 253 J
(e) a= 3.16 m/s^2; K=253 J; Same

(Young, Hugh, and Roger Freeman. University Physics. 12th. San Francisco: Pearson Education, 2008.)