1. A 15 kg cannon ball is red with a muzzle speed of 40m=s making an angle of 53

Question

1. A 15 kg cannon ball is red with a muzzle speed of 40m=s making an angle of 53 degree with the horizontal.(Neglect air resistance.)

(a) What are its initial vertical and horizontal speeds?
(b) On the way up, how long will it take to reach an altitude of 30 m?
(c) How long (measured from the launch point) will it take to reach an altitude of 30m on its way down?
(d) Determine the horizontal and vertical components of the velocity of the ball at an
altitude of 30m on its way down.
(e) How much work is done by gravity on the ball as it moves from its launch point to
an altitude of 30m on its way down.

Explanation / Answer

a) Vh = 40cos53 = 24.07m/s

Vv = 40sin53 = 31.94m/s

B) h = 30 m

in vertical direction

S = ut + 0.5gt2

30 = 31.94t + 0.5 x 9.8t2

4.9t2 + 31.94t - 30 = 0

t = 0.83s

C) it will take same time = 0.83s

D) Vh = 24.07m/s , remains the same bcoz of no accelaration in horizontal idirection

Vv = 31.94 - 9.8 x 0.83

Vv = 23.806 m/s

e)work done = change in PE = mgh = 15 x 9.8 x 30 = 4410 J

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