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A 2 kg mass and a 5 kg mass are connected by a massless rope through a frictionless pulley as shown. If the 5 kg mass descends with a constant velocity of 1.3 m/s, what is the coefficient of kinetic friction, μk, between the 2 kg mass and the surface?
Title
A 2 kg mass and a 5 kg mass are
Your Result
Correct
Difficulty
Hard
Your Pace
0:05
Others' Pace
2:14
Text Explanation
2.5: To begin this question, draw a free-body diagram for both mass as follows:
If we designate the rightward/downward direction as positive, and the leftward/upward direction as negative, keeping in mind that a constant velocity means a net force of zero, we get the following equations:
-μkFN + T = 0
-T + mg = 0
Substituting for T, we get, μkFN = mg. Solving for μk, we get μk = (mg/FN).
FN = (2 kg)(9.8 m/s2) = 20 N
Solving for μk, we get μk = (5)(9.8)/20 = 2.5.
0.3: This answer is incorrect, according to the math above.
0.9: This answer is incorrect, according to the math above.
1.4: This answer is incorrect, according to the math above.
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