# Compressive force on a rod

The ball has a weight of 15 lb and is fixed to a rod having a negligible mass. If it is released from rest when theta = 0 deg., determine the angle theta at which the compressive force in the rod becomes zero (see attachment for an illustration)

answer should be 48.2 deg. Not sure how to get there though.

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The two-pages solution shows step by step how to utilize conservation of energy to obtain the critical angle.

Elastic Moduli and Pascal's Principle and Fluid Dynamics

Question 1: A bimetallic rod is composed of brass and copper.

a. If the rod is subjected to a compressive force, will the rod bend toward the brass or the copper? Why?

b. Justify your answer mathematically if the compressive force is 5.00 X 104 N.

Question 2: A water dispenser for pets has an inverted plastic bottle. When a certain amount of water is drunk from the bowl, more water flows automatically from the bottle into the bowl. The bowl never overflows. Explain the operation of the dispenser. Does the height of the water in the bottle depend on the surface area of the water in the bowl?

Question 3: A 75-Kg athlete does a single-hand handstand. If the area of the hand in contact with the floor is 125 cm2, what pressure is exerted on the floor?

Question 4: What is the fractional decrease in pressure when a barometer is raised 35 m to the top of a building? (Assume that the density of air is constant over that distance.)

Question 5: An oak barrel with a lid of area 0.20 m2 is filled with water. A long, thin tube of cross-sectional area 5.0 X 10-5 m2 is inserted into a hole at the center of the lid, and water is poured into the tube. When the water reaches 12 m high, the barrel bursts.

a. What was the weight of the water in the tube?

b. What was the pressure of the water on the lid of the barrel?

c. What was the net force on the lid due to the water pressure?

Question 6: A hypodermic syringe has a plunger of area 2.5 cm2 and a 5.0 X 10-3 cm2 needle.

a. If a 1.0-N force is applied to the plunger, what is the gauge pressure in the syringe's chamber?

b. If a small obstruction is at the end of the needle, what force does the fluid exert on it?

c. If the blood pressure in a vein is 50 mm Hg, what force must be applied on the plunger so that fluid can be injected into the vein?

See attached file for full problem description.

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