Sir Dudley the Dextrous is loading cannons on top of the castle\\\'s tallest tow

Question

Sir Dudley the Dextrous is loading cannons on top of the castle's tallest towers in preparation for an expected attack. He slips, and a 2.00 kg cannonball rolls to the edge of the tower (which has a perfectly horizontal surface), and falls to the ground below. It takes the cannonball 2.15 seconds to fall to the ground, and air resistence is negligible. How much work is done by gravity on the falling cannonball?

During the fall, what is the average power transfer to the cannonball due to the force of gravity?

Explanation / Answer

Using the equation of motion :

s = ut + 0.5*at^2

For vertical motion,

u = initial vertical speed = 0

a = 9.8 m/s2

s = vertical height of the tower

So, s = 0 + 0.5*9.8*2.15^2

So, s = 22.65 m

So, by falling s = 22.65 m, the work done by gravity = m*g*s

= 14*9.8*22.65 = 3107.6 J <-----------answer

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