A cannonball, mass m = 20kg, it shot out of a cannon at an angle of 65 degree wi
ID: 1570857 • Letter: A
Question
A cannonball, mass m = 20kg, it shot out of a cannon at an angle of 65 degree with respect to the horizontal, with an initial speed of 20m/s. It is shot from level ground, and returns to level ground.. (Ignore air drag) (a) Obtain the initial kinetic energy, so just at it is fired. (b) Obtain the kinetic energy at the peak of the trajectory, i.e., at the maximum height. (c) Obtain the potential energy due to gravity at the maximum height. (d) How much work has been done on the ball by gravity, from the point it leaves the cannon to its maximum height? (e) Obtain the final kinetic energy, so just before it hits the ground.Explanation / Answer
(a)
initial kinetic energy Ki = (1/2)*m*v^2 = (1/2)*20*20^2 = 4000 J
(b)
kinetic energy at the maimum height K = (1/2)*m*vx^2
vx = v*costheta
k = (1/2)*20*(20*cos65)^2 = 714.42 J
(c)
U = Ki - K = 3285.58 J
(d)
Wg = dU = 3285.58 J
(e)
Kf = ki = 4000 J
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