EXAM 2                      October 29, 1996                          PHYS 207

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g = 9.8 m/sec2Radius of the earth = 6.38 x 106 m The mass of the electron is 9.11 x 10-31 kg.
For all problems, place the equations representing the physics principles you are using in the box on the page. You may use the general form of the equation or the form you get applying the principle to the problem at hand. If no diagram is applicable to a problem, write "none" in the diagram section.

1. (10 points)

The diagram below shows the potential energy of a system. Show on the diagram

(a) a qualitative sketch of the corresponding force; in particular show where the force is positive, negative, and zero.

(b) a quantitative plot of the kinetic energy, if the total energy of the system is 3.5 joules.
2. (From homework, 30 points)

A 3.20-kg block starts at rest and slides a distance d down a frictionless 30.0o incline, where it runs into a spring. The block slides an additonal 21.0 cm before it is brought to rest momentarily by compressing the spring, whose spring constant is K = 431 newtons/meter. What is the value of d?

Diagram:
Principles:

3. (30 points) A mass tied to a string swings around in a horizontal circle of radius R with the string keeping a constant angle to the vertical. The mass travels at a speed of v. What is the angle of the string from the vertical in terms of v, R, and the local value of g? 

Diagram:
Principles:

4. (30 points) In the diagram below, assume that the force F is exactly the right size so that the mass M3 remains at a fixed height. All surfaces are frictionless. What is the tension in the rope? How big is F?

Principles:

Use this page if necessary to continue any of the problems. Be sure to label the problem number.