Physics CYU Work and Energy

Ben Travlun carries a 200-N suitcase up three flights of stairs (a height of 10.0 m) and then pushes it with a horizontal force of 50.0 N at a constant speed of 0.5 m/s for a horizontal distance of 35.0 meters. How much work does Ben do on his suitcase during this entire motion?

The motion has two parts: pulling vertically to displace the suitcase vertically (angle = 0 degrees) and pushing horizontally to displace the suitcase horizontally (angle = 0 degrees). For the vertical part, W = (200 N) * (10 m) * cos (0 deg) = 2000 J. For the horizontal part, W = (50 N) * (35 m) * cos (0 deg) = 1750 J. The total work done is 3750 J (the sum of the two parts).

A student with a mass of 80.0 kg runs up three flights of stairs in 12.0 sec. The student has gone a vertical distance of 8.0 m. Determine the amount of work done by the student to elevate his body to this height. Assume that his speed is constant.

The student weighs 784 N (Fgrav= 80 kg * 9.8 m/s/s). To lift a 784-Newton person at constant speed, 784 N of force must be applied to it (Newton's laws). The force is up, the displacement is up, and so the angle theta in the work equation is 0 degrees. Thus, W = (784 N) * (8 m) * cos (0 degrees) = 6272 Joules

How much work is done by an applied force to lift a 15-Newton block 3.0 meters vertically at a constant speed?

To lift a 15-Newton block at constant speed, 15-N of force must be applied to it (Newton's laws). Thus, W = (15 N) * (3 m) * cos (0 degrees) = 45 Joules