Homework Answers

2. A barrel contains a 0.120 m layer of oil floating on water that is 0.250 m deep. The density of the oil is 600 kg/m³. What is the gauge pressure at the oil- water interface and at the bottom of the barrel?

1. A 60 kg woman walking through an alley accidentally broke the heel of her left high-heeled

shoes. Now the woman tries to balance on one heel of a pair of high-heeled shoes. If the heel is circular and has a radius of 0.500 cm, what pressure does she exert on the floor?

10. A 2.50-kg rock is attached at the end of a thin, very light rope 1.45 m long. You start it

swinging by releasing it when the rope makes an 11° angle with the vertical. You record the observation that it rises only to an angle of 4.5° with the vertical after swings. (a) How much energy has this system lost during that time? (b) What happened to the "lost" energy? Explain how it could have been "lost."

7. In a physics lab, you attach a 0.200-kg air-track glider to the end of an ideal spring of

negligible mass and start it oscillating. The elapsed time from when the glider first moves

through the equilibrium point to the second time it moves through that point is 2.60 s.

Find the spring's force constant.

6. A machine part is undergoing SHM with a frequency of 5.00 Hz and amplitude 1.80 cm.

How long does it take the part to go from x=0 to x=-1.80 cm.

5. In a materials testing laboratory, a metal wire made from a new alloy is found to break when a tensile force of 90.8 N is applied perpendicular to each end. If the diameter of the wire is 1.84 mm, what is the breaking stress of the alloy?

4. A nylon rope used by mountaineers elongates 1.10 m under the weight of a 65.0-kg climber. If the rope is 45.0 m in length and 7.0 mm in diameter, what is Young's modulus for nylon?

3. A circular steel wire 2.00 m long must stretch no more than 0.25 cm when a tensile force of 400 N is applied to each end of the wire. What minimum diameter is required for the wire?

1. A 0.120-kg, 50.0-cm-long uniform bar has a small 0.055-kg mass glued to its left end and a small 0.110-kg mass glued to the other end. The two small masses can each be treated as point masses. You want to balance this system horizontally on a fulcrum placed just under its center of gravity. How far from the left end should the fulcrum be placed?

A large turntable rotates about a fixed vertical axis (hum1200 kg/m²) making 1 revolution in 6.0 s. A 40-kg student initially standing at the center of the turntable, nuns out along a radius. What is the angular speed of the turntable when he is 2.0m from the center?