FIGURE P5.49 Problems 49 and 50.
Suppose the system of blocks in Problem 49 is initially held motionless and, when released, begins to accelerate. a. If m1 = 7.00 kg, m2 = 2.00 kg, and the magnitude of the acceleration of the blocks is 0.134 m /s2, find the magnitude of the kinetic frictional force between the second block and the ledge. b. What is the value of the coefficient of kinetic friction between the block and the ledge?
(a)
What is the kinetic friction force between the second block and ledge?
Answer to Problem 50PQ
The kinetic friction force between the second block and ledge is
Explanation of Solution
The free body diagram is given below.
Applying Newton’s laws.
Here,
Here,
Write the equation for gravitational force.
Here,
Conclusion:
Using equation III find the gravitational force on each object.
From the free body diagram the find the value of
Substitute the above values and
Substitute above values in equation II to get friction force.
Therefore, the kinetic friction force between the second block and ledge is
(b)
Find the coefficient of kinetic friction force between the block and ledge.
Answer to Problem 50PQ
The coefficient of kinetic friction force between the block and ledge is
Explanation of Solution
Applying Newton’s laws for y direction on block 2.
Here,
Write the equation for friction force.
Here,
Conclusion:
From the free body diagram the find the value of
Substitute
Substitute
Therefore, the coefficient of kinetic friction force between the block and ledge is
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Chapter 5 Solutions
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