1)Starting from rest, a ball of mass 6 kg experiences a constant force of 18 N .
ID: 1629215 • Letter: 1
Question
1)Starting from rest, a ball of mass 6 kg experiences a constant force of 18 N. What is the final kinetic energy (in J) of the ball after it has traveled a distance of 24 m?
2)A ball of mass 1 kg is uniformly accelerated from rest and travels 16 m in 4 s. What is its final kinetic energy (in J) after 4 s?
3)A hockey puck (mass = 3.5 kg) leaves the players stick with a speed of 22 m/s and slides on the ice before coming to rest. The coefficient of friction between the puck and the ice is 0.7. What is the magnitude of the acceleration of the puck due to this friction force? _____ m/s2
Explanation / Answer
1) From work-energy theorem,
Work done= change in KE
F d = m (vf^2)/2 - m vi^2 /2
18 x 24 = KE - 0
KE = 432 J
2) d = u t + a t^2 /2
16 = 0 + a(4^2)/2
a = 2 m/s^2
v = u + a t = 0 + (2 x 4) = 8 m/s
Ke = m v^2 /2 = 1 x 8^2 / 2 = 32 J
3) friction force, f = uk N = uk m g
a = - f/m = - uk g = -.7 x 9.8 = - 6.86 m/s^2
magnitude = 6.86 m/s^2
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