1. Read all of CH 4.There are a lot of ideas and concepts in this chapter, most of which you have been introduced to experimentally in the lab. You must read this chapter carefully and go over all the other examples if you are to understand how to apply Newton's three laws.  Look carefully at examples to see how forces are drawn, FBD are used (see examples 4-10 on pg 99 and 4-13 on pg 104) and Newton's Laws are applied.

2. Do Homework for Unit 9-10: Newton's Laws from the lab Manual.

3.  Do Unit 7 Question below.

4. Do problems 17, 27and 37, in the text. In Q27 be sure to draw FBD of each object and list all the third law pairs. 

Unit 7 Problem

7-2a)  A raindrop falls from a tall building. Draw the forces acting on the drop at three different times as it falls. Include velocity and acceleration vectors also.

            1. As soon as it begins to fall.

            2. After it has fallen some time but is still accelerating.

            3. After the drop has stopped accelerating.

            Explain what is going on at each time.

b)  For an instant two raindrops are falling side by side with the same velocity. One of them is at its terminal velocity, while the other is not. Draw the force, velocity and acceleration vectors next to both raindrops and explain which one must be at terminal velocity and which will reach the ground first.

Assignment 2 due Monday June 25th:     

1. Read the text: Chapter 4 again including the more complicated situations discussed like frictional forces on an incline and objects connected with ropes and pulleys. Look carefully at examples to see how forces are drawn, FBD use and Newton's Laws applied.

2. Do Homework for Unit 12. 

3. Do assigned FBD questions on the handout and problems 8-1 to 8-3 below. For all these problems it is important to state Newton's First or Second Law, whichever is appropriate, as a starting point.

4. Do problems 41 and 65 in the text. Be sure to draw FBD of each object and list all the third law pairs. 

You will have difficulty with these problems if you do not first draw clear free body diagrams, write down the equations for N's 2nd Law for the objects before trying to get the answer. Make sure that before asking for help with these problems you have at least got that far. The strategy is discussed on page 93 in your text and I will go over that in class. I would like you to use a template and a draw clear FBD for each object. Don't forget to first determine the x and y axes you are going to use and then write down the 2nd law for each object in both the x and y directions. In grading I will look for the application of a systematic method in solving these problems so a correct answer is not sufficient.

UNIT 8 PROBLEMS

 8-1) Wanda is working out with weights and manages to lift light rope with a 10 kg mass hanging from it quite far. When she is through lifting the right side of the rope and the left side of the rope each make an angle of Ø = 15 deg with respect to the horizontal. (a) Draw a free body diagram showing each of the forces on rope at its midpoint where it is the lowest. (b) What are the magnitudes of the each of her pulling forces F₁ and F₂? (c) How hard would Wanda have to pull with each hand to raise the 10 kg mass so that the rope is be perfectly horizontal?

8-2) A person exerting a horizontally directed force, P, presses a block of mass m against a vertical wall as shown below. It is observed that the block does not slide up or down; it remains at rest in the original position.

a) Draw separate force diagrams showing (1) the block, with all the forces acting on it, (2) the forces acting on the wall in the region of contact with the block and, (3) the earth and its interaction with the block. Describe each force in words (stating what object exerts this force on what) and identifying third law pairs.
b) How do you account in your force diagram, for the fact that the block does not slide down along the wall? Describe three separate changes in this situation each of which would lead, without any other changes, to a condition in which the block starts sliding down the wall.
c) Suppose m and the coefficient of friction are known quantities. Describe how you would calculate the value of the force P that is just sufficient to keep the block from sliding. First obtain an algebraic solution of the problem. Now calculate the force P needed to support a block with a mass of 2kg if the coefficient of friction between the block and the wall is 0.20 .
(This question is taken from Homework and Questions for Introductory Physics Teaching by A. Arons

8-3) An overweight (300lb) crazed man jumps from a 40 m high building (I think its because he supports the Cleveland Indians and the Cleveland Browns a) what is his velocity be just as he hits the ground? b) assuming the impact time is 0.1seconds what is his acceleration? c) What average force does the ground exert on him during impact? Draw a free body diagram of the ball and show velocity and acceleration vectors during impact.

If you have any questions or comments please e-mail bellis@marshall.edu