# Force, acceleration, coefficient of kinetic friction

See attached file for the graph.

In the figure below, m1 = 10.7 kg and m2 = 4.15 kg. The coefficient of kinetic friction is 0.271. If the system is set in motion with m2 moving downward, what will be the acceleration of the system?

I'm not sure how to factor in the coefficient of kinetic friction. Can you show me how to do this problem?

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#### Solution Preview

Here is the solution (in the attached identical files: one pdf the other MS-word)

However some general guidelines to an "algorithmical" way to solve this kind of problems.

1. Choose direction of motion for ...

#### Solution Summary

With graphics and good explanations, the problem is solved.

Basic Physics Problems (Force; Newton's Second Law; Horizontal Force; Net Force; Static Friction; Kinetic Friction)

I would like for you to show me all of your work/calculations and the correct answer to each problem.

15. A 5.0-kg block at rest on a frictionless surface is acted on by forces F1 = 5.5 N and F2 = 3.5 N. What additional horizontal force will keep the block at rest?

19. The engines of most rockets produce a constant thrust (forward force). However, when a rocket is fired into space, its acceleration increase with time as the engine continues to operate. Is this situation a violation of Newton's second law? Explain.

23. What is the mass of an object that accelerates at 3.0 m/s[squared] under the influence of a 5.0-N net force?

29. What is the weight of an 8.0-kg mass in newtons? How about in pounds?

33. A horizontal force of 12 N acts on an object that rests on a level, frictionless surface on the Earth, where the object has a weight of 98 N. (a) What is the magnitude of the acceleration of the object? (b) What would be the acceleration of the same object in a similar situation on the Moon?

35. When a horizontal force of 300 N is applied to a 75.0-kg box, the box slides on a level floor, opposed by a force of kinetic friction of 120 N. What is the magnitude of the acceleration of the box?

39. A jet catapult on an aircraft carrier accelerates a 2000-kg plane uniformly from rest to a launch speed of 320 km/h in 2.0 s. What is the magnitude of the net force of the plane?

49. In an Olympic figure-skating event, a 60-kg male skater pushes a 45-kg female skater, causing her to accelerate at a rate of 2.0 m/s[squared]. At what rate will the male skater accelerate? What is the direction of his acceleration?

53. The weight of a 500-kg object is 4900 N. (a) When the object is on a moving elevator, its measured weight could be (1) zero, (2) between zero and 4900 N, (3) more than 4900 N, or (4) all of the preceding. Why?

(b) Describe the motion if the object's measured weight is only 4000 N in a moving elevator.

59. A girl pushes a 25-kg lawn mower. If F = 30 N and 0 = 37 degrees, (a) what is the acceleration of the mower, and (b) what is the normal force exerted on the mower by the lawn? Ignore friction.

65. A 3000-kg truck tows a 1500-kg car by a chain. If the net forward force on the truck by the ground is 3200 N, (a) what is the acceleration of the car, and (b) what is the tension in the connecting chain?

83. A 40-kg crate is at rest on a level surface. If the coefficient of static friction between the crate and the surface is 0.69, what horizontal force is required to get the crate moving?

87. A hockey player hits a puck with his stick, giving the puck an initial speed of 5.0 m/s. If the puck slows uniformly and comes to rest in a distance of 20 m, what is the coefficient of kinetic friction between the ice and the puck?

93. While being unloaded from a truck, a 10-kg suitcase is placed on a flat ramp inclined at 37 degrees. When released from rest, the suitcase accelerates down the ramp at 0.15 m/s[squared]. What is the coefficient of kinetic friction between the suitcase and the ramp?

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