Solve the following problems on your own paper. Please:

• Show all work.
• Put a box around your final answer to each problem.
• Be sure proper significant figures (SF) used for all answers.
• Separate all solutions with a horizontal line on your paper.
• A random selection of four even problems will be graded for 25 points each.
• Solutions for suggested odd problems can be seen by following links.
• Solutions for even problems will be linked from this page after the due date.

Chapter 4

#2

Answer with 2 SF.

#6

Use mks units when solving this one and answer with 2 SF.

#12

This is very similar to Ch 3, #20. Answer with 2 SF.

#20

Use the leg as the focus of this problem, much like we use the intersection of the ropes as the focus is problem #17. If the sum the x and y components of the forces acting on the leg, setting each equal to zero since the leg is not accelerating, then you will have two equations and two unknowns.

#28

In problems like this, I recommend you determine the direction of motion and take that to be the positive direction for both masses. So here, the direction up the ramp is positive for the 5-kg mass, and down is positive for the 10-kg mass. Sum the forces acting on each mass, and you should end up with two equations and two unknowns.

#38

Again, determine the direction of motion and take that to be the positive direction for both masses. The math here is much easier than in #28, but it is a similar type of problem.

#40

The first part of this problem is a threshold problem. You need to assume the force of static friction is unknown and solve for it. THEN compare your value to the maximum possible value for the force of static friction to answer the question of whether the system moves. In (b), we just assume it is in motion the whole time so just use the force of kinetic friction.

#48

Like problems #41 and #47, the normal force here is not just equal to the weight or the component of weight perpendicular to the surface. You have to include all of the perpendicular forces to correctly solve for the normal force.

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Suggested odd problems:

#1, #3, #5a, #5b, #7, #9, #10, #11, #13, #15, #16, #17a, #17b, #18, #19, #21, #23, #24, #25, #30, #34, #35, #36a, #36b, #39, #41, #45, #47, #50a, #50b, #51, #54, #57a, #57b, #59, #60, #61a, #61b, #62, #66a, #66b