1. A 69.0-kg ice skater is moving at 4.10 m/s when she grabs the loose end of a
ID: 1394060 • Letter: 1
Question
1. A 69.0-kg ice skater is moving at 4.10 m/s when she grabs the loose end of a rope, the opposite end of which is tied to a pole. She then moves in a circle of radius 0.860 m around the pole.
(a) Determine the magnitude of the force exerted by the horizontal rope on her arms. (kN)
(b) Compare this force with her weight.
F rope / W = ??
2. A potter's wheel moves uniformly from rest to an angular speed of 0.21 rev/s in 30.0 s.
(a) Find its angular acceleration in radians per second per second. (rad/s^2)
Help me on three questions on Physics. Thanks
Explanation / Answer
1)
a) F = m*v^2/r
= 69*4.1^2/0.86
= 1349 N
= 1.349 kN
b) F_rope/W = 1349/(69*9.8)
= 1.995
2)
a) w1 = 0
w2 = 0.21*2*pi = 1.32 rad/s
angular acceleration, alfa = (w2-w1)/t
= (1.32-0)/30
= 0.044 rad/s^2
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