physics 100 prac exam#3 Student: ___________________________________________________________________________

1.

An isolated object is initially spinning at a constant speed. Then, although no external forces act upon it, its rotational speed increases. This must be due to A. an increase in the moment of inertia. B. an increase in the mass. C. an increase in the angular momentum. D. a decrease in the moment of inertia. E. impossible, angular momentum conservation is violated.

2.

Three horses are side-by-side on a merry-go-round: one at the edge, one near the axis, and one in between. Each horse has the same angular speed. Which horse has the greatest linear speed? A. The horse nearest the axis. B. The horse in the middle. C. The horse at the edge. D. The linear speed is the same for all three horses.

3.

A sphere and a hoop have the same diameter and the same mass. Which one will have a larger rotational inertia? A. The sphere. B. The hoop. C. Both will require the same time to reach the bottom.

4.

A torque acting on a body tends to produce A. equilibrium. B. linear velocity. C. a new center of gravity. D. angular rotation.

5.

The rotational inertia of an object depends on A. its color. B. how fast it is spinning. C. the amount of torque applied to it. D. how its mass is distributed about the spin axis. E. none of these.

6.

Using a longer-handled wrench to loosen a tight nut allows you to A. exert more force on the nut. B. increase the moment of inertia of the nut. C. apply more torque to the nut. D. pull harder on the wrench.

7.

A figure skater is spinning with her arms extended. She now pulls her arms close to her body. What happens? A. Her rotational inertia decreases. B. The net torque on her increases. C. Her lever arm gets shorter. D. Her angular acceleration decreases.

8.

A solid disk and a hollow disk with the same mass and diameter are released together (from rest) to roll down an incline. The solid disk reaches the bottom first. From this information we can say that the angular acceleration was A. larger for the solid disk. B. larger for the hollow disk. C. the same for both disks. D. impossible to know without a measurement of time.

9.

Archimedes' Principle states that A. the pressure in a fluid is directly related to the depth below the surface of the fluid. B. an object immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. C. the pressure of a fluid is inversely proportional to the temperature of the fluid. D. the velocity of a fluid is directly proportional to the pressure exerted on the fluid.

10. A child is drinking a liquid with a straw. Which of the following statements is true? A. The fluid is being pulled up into the straw. B. Longer straws work better because the pressure is larger deeper down. C. The pressure inside the straw depends on the viscosity of the liquid. D. The pressure in the straw is reduced and the liquid is pushed upward by atmospheric pressure on the surface of the liquid. 11. If you hold a light tissue in your hands and gently blow across its top, the tissue will rise slightly because A. the pressure of moving air is less than that of static air. B. collisions of the moving air with the tissue cause it to rise. C. blowing across the tissue removes all of the air, and then the air below the tissue pushes the tissue up. D. according to Archimedes' Principle, moving air exerts more buoyant force. 12. An ice cube in a glass of water is pushed to the bottom of the glass and held there with a straw. Consequently, the buoyant force on the ice cube is now A. exactly balanced by the force exerted by the straw. B. exactly balanced by the weight of the ice cube. C. the same as when the cube was floating at the top. D. greater than when the cube was floating at the top. 13. If the atmospheric pressure is 15 lb/in2, what is the corresponding downward force on the top of a horizontal square area 6 inches on each side? A. 540 lbs. B. 90 lbs. C. 15 lbs. D. zero. 14. Three individuals stand with all of their weight on the heel of one foot: a man of weight 600 N and a heel area of 100 cm2, a child of weight 200 N and a heel area of 25 cm2, and woman of weight 450 N and a heel area of 2 cm2. The one exerting the least pressure on the ground is A. the man. B. the child. C. the woman. D. All exert the same. 15. A penny, a quarter, and a silver dollar lie at the bottom of a wishing well filled with water. The coin experiencing the largest downward force on its top surface due to the water pressure is the A. penny. B. quarter. C. silver dollar. D. All experience the same downward force.

16. A gas originally occupies a volume of 0.5 m3 at a pressure of 100 kPa. It is slowly allowed to expand until the volume is 2.5 m3. Assuming the temperature is kept constant, the final pressure will be A. 10 kPa. B. 20 kPa. C. 50 kPa. D. 100 kPa. E. 500 kPa. 17. The temperature of a sample of a substance is a way to gauge A. the average kinetic energy of the molecules in that sample. B. the kinetic energy of the fastest moving molecule in the sample. C. the average momentum of the molecules in a sample. D. the average momentum of the fastest 50% of the molecules in the sample. 18. Heat is a form of energy, and it has long been known that heat energy will naturally flow A. from cold to hot objects. B. from hot to cold objects. C. from solids to liquids, but only when the solid is melting. D. from liquids to solids, except when the solid is melting. 19. On a cold winter's morning you awake and step out of bed. One foot is on the tile floor and the other is on a rug on the floor. Which statement is true? A. The tile feels colder because it is smoother than the rug. B. The tile feels colder because it conducts heat more rapidly away from your foot. C. The tile feels colder because it is connected to the cold ground outside. D. The tile feels colder because it cannot absorb water like the rug can. 20. When the temperature of the air in a balloon is raised, the volume of the balloon A. increases. B. stays the same. C. decreases. D. expands. 21. A mixture consists of 50 g of ice and 60 g of liquid water, both at 0°C. The amount of heat that must be added to melt all of the ice is about A. 4000 cal. B. 4800 cal. C. 21,600 cal. D. 32,400 cal. 22. While studying for this quiz you realize that you still have 100 g of lukewarm coffee at 40°C left in a paper cup. When you pour 50 g of boiling water into the cup, the temperature of the resulting coffee-like mixture will be now A. 50°C. B. 60°C. C. 67°C. D. 70°C. E. 80°C. 23. The temperature of 100 g of water is to be raised from 10°C to 60°C. The energy needed to do this is about A. 1 × 103 cal. B. 5 × 103 cal. C. 6 × 103 cal. D. 8 × 103 cal. E. 5.4 × 104 cal.

24. Four samples of steel, lead, alcohol, and glass all have the same mass and are all initially at 20°C. After 100 calories of heat are added to each sample, the final temperatures are 38.2°C for the steel, 85.6°C for the lead, 23.4°C for the alcohol, and 30°C for the glass. Which of these four materials has the largest specific heat capacity? A. The steel. B. The lead. C. The alcohol. D. The glass. E. All have the same heat capacity, since all absorbed 100 cal of heat. 25. An electron situated near another electron would feel A. a repulsive electrical force. B. an attractive electrical force. C. a repulsive magnetic force. D. an attractive magnetic force. E. no forces from the other electron. 26. Compared to the magnitude of the charge on a proton, the magnitude of the electrical charge carried by an electron is A. about the same. B. exactly the same. C. only 1/2 as large. D. only 1/3 as large. 27. A strip of fur is rubbed against a hard rubber rod. The rod thereby acquires a negative charge because A. frictional forces create electrons. B. rubbing caused electrons to move from the fur to the rod. C. friction caused protons to be removed from the rod. D. electrons from the air molecules are transferred to the rod. 28. If the distance between two spherical charged objects decreases by a factor of two, then the electrical force between the objects A. decreases by a factor of four. B. is half as big. C. does not change. D. doubles. E. increases by a factor of four. 29. If the potential at point A is one volt it means that A. an object at A has charge equal to one coulomb. B. an electron at A can perform one Joule of work. C. there is a small battery present. D. a charge at A has potential energy one joule for each coulomb of charge. 30. Two equal charges repel one another with a force of 4.0 × 10-4 N when they are 10 cm apart. If they are moved until the separation is 2.5 cm, the repulsive force will be A. 0.25 × 10-4 N. B. 1.0 × 10-4 N. C. 4.0 × 10-4 N. D. 16 × 10-4 N. E. 64 × 10-4 N. 31. A positive charge is fixed at the origin. A negative charge is moved along the x-axis from x = 50 cm to x = 10 cm. The potential energy of the negative charge A. does not change. B. increases. C. decreases.

32. A uniform electric field has a magnitude of 10 N/C and is directed upward. A charge brought into the field experiences a force of 5.0 N downward. The charge must be A. +50 C. B. -50 C. C. +0.5 C. D. -0.5 C. E. -2.0 C. 33. A household circuit rated at 120 volts is protected by a fuse rated at 15 amps. What is the maximum number of 100 watt light bulbs which can be lit simultaneously in parallel in this circuit without blowing the fuse? A. 4 B. 8 C. 18 D. 20 E. 24 34. The current (measured in amperes) in a circuit is A. the amount of charge (measured in Coulombs) that passes a point (in the circuit) in 1 second. B. the amount of the total energy carried by 1 Coulomb of charge. C. the total number of electrons in the circuit. D. never lethal if the current is due to positive charges. 35. A 40 W bulb and a 60 W bulb are connected in series with a 120 V power source. Which of the following is true for this arrangement? A. The 40 W bulb is brighter than the 60 W bulb. B. The 60 W bulb is brighter than the 40 W bulb. C. The 60 W bulb is brighter than it would be if the 40 W bulb were replaced by a wire. D. The 40 W bulb is brighter than it would be if the 60 W bulb were replaced by a wire. 36. What is the best way to ensure that a 40 watt bulb and a 60 watt bulb have the same current within them? A. Connect the bulbs in series with the power supply, like this:

B. Connect the bulbs in parallel with the power supply, like this:

C. Separately connect the bulbs to two batteries having the same voltage. D. It can't be done: different wattage bulbs must always have different currents. 37. In many ways, an electric circuit is like the plumbing system in your home. The voltage on an electric circuit corresponds to the ________ in a plumbing system. A. drain B. trap C. pressure D. faucet or valve 38. A 9 ohm resistor and a 16 ohm resistor are connected in series in a circuit with a 4.0 volt battery. Assuming negligible internal resistance in the battery, the current in the 12 ohm resistor will be A. 0.33 A. B. 0.5 A. C. 1.0 A. D. 12 A. E. 0.16 A.

39. A 12 ohm resistor and a 24 ohm resistor are connected in parallel across a 6.0 V battery. The correct statement from the following is A. the current is the same in each resistor. B. the power dissipated is the same in each resistor. C. the voltage difference between the ends of each resistor is the same. D. the larger current is in the larger resistor. 40. An electric iron uses 9.0 A of current and has a power rating of 1100 W. The resistance of the iron is A. 0.0082 Ω. B. 0.074 Ω. C. 14 Ω. D. 120 Ω.

physics 100 prac exam#3 Key 1. D 2. C 3. B 4. D 5. D 6. C 7. A 8. A 9. B 10. D 11. A 12. D 13. A 14. A 15. C 16. B 17. A 18. B 19. B 20. A 21. A 22. B 23. B 24. C 25. A 26. B 27. B 28. E 29. D 30. E 31. C 32. D 33. C 34. A 35. A 36. A

37. C 38. E 39. C 40. C

physics 100 prac exam#3 Summary Category Griffith - Chapter 08 Griffith - Chapter 09 Griffith - Chapter 10 Griffith - Chapter 12 Griffith - Chapter 13

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