An object with a mass of m = 5.5 kg is attached to the free end of a light strin
ID: 1264615 • Letter: A
Question
An object with a mass of m = 5.5 kg is attached to the free end of a light string wrapped around a reel of radius R = 0.240 m and mass of M = 3.00 kg. The reel is a solid disk, free to rotate in a vertical plane about the horizontal axis passing through its center as shown in the figure below. The suspended object is released from rest 5.90 m above the floor.
(a) Determine the tension in the string.
N
(b) Determine the magnitude of the acceleration of the object.
m/s2
(c) Determine the speed with which the object hits the floor.
m/s
Explanation / Answer
I = 1/2 mR^2
I = 1/ 2 * 3 * 0.24^2
I = 0.0864 Nm^2
Tension T = mg-ma
Torque ? = T*R
? = (mg - ma)*R (1)
? = I*?
? = I*(a/R) (2)
equating 1 and 2
a = mg/(I/R^2 + m)
a = 5.5 * 9.81 / (0.0864 / 0.24^2 + 5.5)
a = 7.70 m/s^2
acceleration of the object = 7.70 m/s^2
Tension T = mg-ma
Tension = 5.5 * (9.81 - 7.7)
tension in the string = 11.605 N
v = sqrt(2sa)
v = sqrt(2 * 5.9 * 7.7)
v = 9.532 m/s
speed with which the object hits the floor = 9.532 m/s
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