13 March 2013

Physics Homework Ch9

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1. The British gold sovereign coin is an allow of gold and copper having a total mass of 7.988  g, and is 22-karat gold.
a) Find the mass of gold in the sovereign in kilograms using the fact that the number of karats = 24 x (mass of gold)/(total mass)
__________ kg

b) Calculate the volumes of gold and copper, repsectively, used to manufacture the coin
volume of gold     _______ m3
volume of copper _______ m3

c) Calculate the density of the British sovereign coin.
________ kg/m3

2. Calculate the mass of a solid gold rectangular bar that has dimensions /wh = 5.20 cm x 14.0 cm x 29.0 cm. (The density of gold is 19.3 x 103 kg/m3
_________ kg

3. The four tires of an automobile are inflated to a gauge pressure of 2.3 x 105 Pa. Each tire has an area of 0.024 m2 in contact with the ground. Determine the weight of the automobile
_______ N

4. A 220-kg load is hung on a wire of length of 3.30 m, cross-sectional area 2.00 x 10-5 m2, and Young's modulus 8.00 x 1010 N/m2. What is its increase in length?
________ mm

5. A plank 2.00 cm thick and 16.1 cm wide is firmly attached to the railing of a ship by clamps so that the rest of the board extends 2.00 m horizontally over the sea below. A man of mass 90.0 kg is forced to stand on the very end. If the end of the board drops by 5.30 cm because of the man's weight, find the shear modulus of the wood.
_______ Pa

6. Bone has a Young's modulus of about 1.80 x 1010 Pa. Under compression, it can withstand a stress of about 1.65 x 108 Pa before breaking. Assume that a femur (thigh-bone) is 0.58 m long, and calculate the amount of compression this bone can withstand before breaking.
________ mm

Watch the professor work a very similar problem

7. The spring of pressure gauge shown in the figure below has a force constant of 1,080 N/m, and the piston has a radius of 1.40 cm. As the gauge is lowered into water, what change in depth causes the piston to move in by 0.750 cm?
_______ m

a) Calculate the absolute pressure at the bottom of a fresh-water lake at a depth of 22.8 m. Assume the density of the water is 1.00 x 103 kg/m3 and the air above is at a pressure of 101.3 kPa.
_______ Pa

b) What force is exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diamter of 30.6 cm?
_______ N

9. The figure below shows the essential parts of a hydraulic brake system. The area of the piston in the master cylinder is 1.8 cm2 and that of the piston in the brake cylinder is 6.4 cm2. The coefficient of friction between the shoe and wheel drum is 0.50. If the wheel has a radius of 41 cm, determine the frictional torque about the axle when a force of 48 N is exerted on the brake pedal.
______N * m

10.A small ferryboat is 4.00 m wide and 6.00 m long. When a loaded truck pulls onto it, the boat sinks an additional 4.20 cm into the river. What is the weight of the truck?
______ N

See the professor work a similar problem

11. A spherical weather balloon is filled with hydrogen until its radius is 3.10 m. Its total mass including the instruments it carries is 13.0 kg

a) Find the bouyant force acting on the balloon, assuming the density of air is 1.29 kg/m3

b) What is the net force acting on the balloon and its instruments after the balloon is released from the ground?

c) Why does the radius of the balloon tend to increase as it rises to higher altitude
  - Because the external pressure (increases/decreases) with increasing altitude (choose one)

12. The gravitational force exerted on a solid object is 5.05 N as measured when the object is suspended from a spring scale as in Figure (a). When the suspended object is submerged in water, the scale reads 3.82 N (Figure (b)). Find the density of the object.
______ kg/m3

13. Water flowing through a garden hose of diameter 2.71 cm fills a 24.0-L bucket in 1.10 min.

a) What is the speed of the water leaving the end of the hose?
______ m/s

b) A nozzle is now attached to the end of the hose. If the nozzle diameter is one-third the diameter of the hose, what is the speed of the water leaving the nozzle?
______ m/s

14. A liquid (ρ = 1.65g/cm3) flows through a horizontal pipe of varying cross section as in the figure below. In the first section, the cross-sectional area is 10.0 cm2, the flow speed is 283 cm/s, and  the pressure is 1.20 x 105 Pa. In the second section, the cross-sectional area is 3.00 cm2

a) Calculate the smaller section's flow speed
______ m/s

b) Calculate the smaller section's pressure
______ Pa

See the professor work a similar problem

15. Water moves through a constricted pipe in steady, ideal flow. At the lower point shown in the figure below, the pressure is 1.70 x 105 Pa and the pipe radius is 2.60 cm. At the higher point located at y = 2.50 m, the pressure is 1.22 x 105 Pa and the pipe radius is 1.30 cm.

a) Find the speed of flow in the lower section
______ m/s

b) Find the speed of flow in the upper section
______ m/s

c) Find the volume flow rate through the pipe.
______ m3/s

See the professor work a similar problem


  1. thank you very much. its really helpful

  2. Seconded, MOB University is truly helpful. Thanks Mike!

    1. Glad you think so. This fall I plan on finishing up the cell biology and starting genetics. Then physics 2 in the spring.
      Best way to show support is share links! ;)

  3. Thank you very much.

  4. Where can we send questions we have from webassign that we would like you to cover in another video?

    1. kparks, I just added a link to the top of this page.
      Submit your questions there.

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  5. Great videos! will share! Do you do Organic chemistry videos?