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Homework #8

Phys 222

Professor: Dr. Tovar Contact Information

Text:Serway & Jewitt1. A 50-kg ball is suspended from a steel wire of length 5 m and radius

2mm. By how much does the wire stretch?2. A force F is applied to a long wire of length L and cross-sectional area

A. Show that if the wire is considered to be a spring, the force constant k is

given by k=AY/L and the energy stored in the wire is PE=1/2 F (Delta L).3. An elevator cable is to be made of a new type of composite developed by

Acme Laboratories. In the lab, a sample of the cable that is 2 m long and has

a cross-sectional area of 0.2 mm2 fails under a load of 1000 N. The cable in the

elevator will be 20 m long and have a cross-sectional area of 1.2 mm2. It will

need to support a load of 20,000 N safely. Will it?

4. If you are given a wire with a circular cross-section of radius r and a length

L, show that (Delta r)/r = -1/2 (Delta L)/L, assuming that (Delta L)<<L. Hint:

the density and volume remain constant.5. 16.5*

6. 16.6*

7. 16.10*

8. 16.12

9. 16.53

10. 16.60

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