Consider two situations. In the first a machine must pull a box up a rough slope

Question

Consider two situations. In the first a machine must pull a box up a rough slope at a constant speed. The mass of the box is M=800kg, the coefficient of kinetic friction is .2 and the slope is inclines at 15 degrees to the horizontal. In the second situation the machine must pull an equally massive wheel up the same slope. The cable is attached to the axle of the wheel and exerts negligible torque about that axis. If both the box and the wheel move up the slope at .5 m/s then how much power (in Watts) must the machine supply for each task.

Explanation / Answer

power = force * velocity
force = force against friction
= N

= *mgsin

= 0.2 * 800 * 9.81 * sin15

= 406.24 N

power = 406.24 * 0.5

= 203.12 W

case-2

here wheel is not rolling so will be treated as a mass same as previous case

so, power supplied is same = 203.12 W

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