# Set of three problems on Newton's laws of motion

1) A window washer of mass M is sitting on a platform suspended by a system of cables and pulleys as shown (see attachment). He is pulling on the cable with a force of magnitude F . The cables and pulleys are ideal (massless and frictionless), and the platform has negligible mass.

Find the magnitude of the minimum force that allows the window washer to move upward. Express your answer in terms of the mass and the magnitude of the acceleration due to gravity .

2) Two blocks with masses M1 and M2 hang one under the other. For this problem, take the positive direction to be upward, and use g for the magnitude of the acceleration due to gravity.

A) Find T2, the tension in the lower rope. Express your answer in terms of some or all of the variables M1, M2 ,and g.

B) Find T1, the tension in the lower rope. Express your answer in terms of some or all of the variables M1, M2 ,and g.

C) Find T2, the tension in the lower rope. Express your answer in terms of some or all of the variables M1, M2 ,a, and g.

D) Find T1 , the tension in the upper rope. Express your answer in terms of some or all of the variables

3) A wedge with an inclination of angle rests next to a wall. A block of mass m is sliding down the plane, as shown (see attachment). There is no friction between the wedge and the block or between the wedge and the horizontal surface.

A) Find the magnitude, Fnet , of the sum of all forces acting on the block. Express Fnet in terms of theta and m along with any necessary constants.

B) Find the magnitude, Fww , of the force that the wall exerts on the wedge. Express in terms of theta and m along with any necessary constants

See attached file for full problem description.

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#### Solution Summary

The problems have been solved step by step to illustrate application of Newton's laws of motion.

Set of 8 conceptual questions and 5 problems on mechanics.

I need help with the following conceptual questions and the problems numbered 2, 4, 32, 36, 38.

1. A friend tells you that since his car is at rest there are no forces acting on it. How would you reply?

6. Riding in an elevator moving with a constant speed, you begin a game of darts. Do you have to aim your darts higher,

lower or the same as when you play darts on solid ground?

20. A surfer hangs ten and acc down the sloping face of a wave. If the surfer acceleration is 3.25 m/s2 and the friction

can be ignored, what is the angle at which the face of the wave is inclined above the horizontal?

25. A 65kg skier speeds down a trail, the surface is smooth and inclined at an 22 degrees with the horizontal.

(a) Find the direction and magnitude of the net force acting on the skier.

(b) Does the net force exerted on the skier increase, decrease, or stay the same as the slope becomes steeper?

37. A 23 kg suitcase is being pulled with constant speed by a handle that is at an angle 25 degrees above the horizontal. If

the normal force exerted on the force is 180 N, what is the force F applied to the handle?

39. A 9.3 kg child sits in a 3.7 kg high chair.

(a) Draw a free body diagram for the child and find the normal force exerted by the chair on the chills.

(b) Draw a free body diagram for the chair and find the normal force exerted by the floor on the chair.

42. Find the normal force exerted on a 2.7 kg book resting on a surface inclined at 32 degrees above the horizontal.

(a) If the angle of the incline is reduced do you expect the normal force to Increase, decrease, or stay the same?

50. Biomechanical research has shown that when a 67 kg person is running, the force exerted on each foot as it strikes the

ground can be as great as 2300 N.

(a) What is the ratio of the force exerted on the foot by the ground to the person's body weight?

(b) If the only forces acting on the person are (i) the force exerted by the ground and (ii) the person's weight, what is

the magnitude and direction of the person's acceleration? C. If the acceleration found in part (b) acts 10.0 ms, what is

the resulting change in the vertical component of the person's velocity?

(For problems please see attachment)

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