It takes a crane 60 seconds to lift a 150kg box from the ground to the top of a 100m tall building. Calculate the magnitude of power exerted by the crane to lift the box A. 9 x 109 W

B. 9 x 109 N

C. 2450 W

D. 2450 N

E. None of the above

Explanation:

Power equals the amount of work done divided by the time it takes to do the work (in seconds). Work itself is equal to the amount of force it takes to move an object a certain number of meters. We are given the mass of the object. Since force is a measure in Newtons, and we are given mass, we need to use the mass to find the weight of the object, since weight is a force and is measured in Newtons!

F = weight = 150(9.8) so

F = 1470. Now we will use that along with the displacement in the Power equation:

P = [1470(100)]/60 so

P = 2450 Watts, choice C.

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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probably not the "magnets"in the magnet, so to speak, are thought to be electrons orbiting in shells. vurrent loops two sides to the loop