A 44.0-kg projectile is fired at an angle of 30.0 degree above the horizontal wi

Question

A 44.0-kg projectile is fired at an angle of 30.0 degree above the horizontal with an initial speed of 1.30 Times 10^2 m/s from the top of a cliff 130 m above level ground, where the ground is taken to be y = 0. What is the initial total mechanical energy of the projectile? Suppose the projectile is traveling 92.1 m/s at its maximum height of y = 306 m. How much work has been done on the projectile by air friction? What is the speed of the projectile immediately before it hits the ground if air friction does one and a half times as much work on the projectile when it is going down as it did when it was going up?

Explanation / Answer

c)

for the work done by friction while coming down ,

work done = 1.5 * (- 1.09*10^5) J

work done = -1.64 *10^5 J

Using conservation of energy and work energy theorum

0.5 * 44 * v^2 = 0.5 * 92.1^2 * 44 + 44 * 9.8 * 130 - 1.64 *10^5

solving for v

v = 59.7 m/s

the speed of the projectile when it ground is 59.7 m/s

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