Equation Sheet for Physics 103 Midterm 1 W = F D. E pot = M g h. E kin = _ M v 2

Transcription

1 Equation Sheet for Physics 103 Midterm 1 Efficiency = Useful Energy Out Total Energy In Efficiency F = M a F = M g s = D t Work Eff = Work out in G M1 M F = 2 D W = F D E pot = M g h E kin = _ M v 2 2 a = v f v i t G = 6.67 x N m 2 /kg 2 1 mile = 5,280 feet = kilometers 1 lb = 4.45 N 1 joule = 0.74 foot pounds g = 9.8 m/s 2 = 32 ft/s 2 1 foot = meters 1 hour = 3600 seconds 1 horsepower = 746 watts 1 kilowatt = 1,000 watts 89

2 Sample midterm 1A 1. If you are driving your car at 40 miles per hour, how long will it take you to drive 10 miles? a) 4 minutes b) 15 minutes c) 30 minutes d) 50 minutes e) 400 minutes 2. One quart of gasoline contains 31,500 BTU's of energy. How many BTU's of energy are contained in 6 quarts of gasoline? a) 5.25 x 10 3 BTU's b) 1.89 x 10 4 BTU's c) 5.25 x 10 4 BTU's d) 1.89 x 10 5 BTU's e) 1.89 x 10 6 BTU's 3. According to Newton's Third Law, the force of the sun on the moon is a) 100 times the force of the moon on the sun. b) 10 times the force of the moon on the sun. c) equal to the force of the moon on the sun. d) equal to the ratio of the mass of the sun to that of the moon. e) equal to the ratio of the mass of the moon to that of the sun. 4. The doubling time for a certain group of cells is ten minutes. If we initially have 10 cells, how many cells do we have 30 minutes later? a) 10,000 cells b) 1,000 cells c) 640 cells d) 320 cells e) 80 cells 80

3 5. (10 3 x 10 4 ) / 10 7 = a) (12 / 7) 10 b) 10 5 c) 10 d) 1 e) 0 6 The diagram below shows the energy input to a device John has invented, along with the energy that actually goes into useful operation of the device and the energy wasted. What is the efficiency of John's invention? Energy In 120 joules Useful Energy Out 48 joules Wasted Energy Out 72 joules a) 10% b) 20% c) 40% d) 60% e) 100% 7. The distance between the sun and the earth, 9.3 x 10 7 miles, is called an astronomical unit (A.U.). If the distance between the sun and Pluto is 3.68 x 10 9 miles, what is this distance in A.U.? a) 40 A.U. b) 250 A.U. c) 2.5 x A.U. d) 3.4 x A.U. e) 3.4 x A.U. 8. Which of the following energy transformations took place when the toy train in class ran around its track? a) electrical to kinetic energy b) gravitational potential to kinetic energy c) kinetic to gravitational potential energy d) electrical to thermal energy e) All of the above energy transformations took place. 81

4 9. Joe, an amateur scientist, wants to build a homemade velocity meter for his car. What components might he need in order to construct such a meter? a) a speedometer b) a compass c) a clock d) all of the above e) both a) and b) 10. Jane has $5,000 to invest, and she must increase that amount to $10,000 in 8 years. At what annual growth rate must she invest her money to achieve the desired outcome? You may wish to refer to the table below. a) 20 % b) 16 % c) 12 % d) 9 % e) 6 % Growth Rates and Doubling Times Annual Growth Rate (in percent) Doubling Time (in years) Annual Growth Rate (in percent) 0 Infinite Doubling Time (in years) 82

5 11. The video The Light Stuff, dealt with the accomplishments of the Daedalus crew in human powered flight. The final 72 mile flight took place in a) the United States. b) Brazil. c) Greece. d) England. e) Germany. 12. A box with a mass of 3 kg is at rest on a rough surface. Susan starts pushing the box with a constant force of 8 newtons, and notices that the velocity of the box increases by 1 m/sec each second. What is the fictional force between the rough surface and the box? a) 1 newton b) 3 newtons c) 5 newtons d) 8 newtons e) Since Susan can move the box, there cannot be any frictional force between the box and the rough surface. 13. Rock A weighs 1 pound and is dropped from a third floor window. Rock B weighs 2 pounds and is dropped from a second floor window. Rock C weighs 3 pounds and is dropped from a first floor window. Neglecting air resistance, which rock would be traveling the fastest just before it hits the ground? a) rock A b) rock B c) rock C d) All three rocks will hit the ground with the same speed. e) There is not enough information given to determine the answer. 14. The video Ring of Truth, Change discussed the food used as an energy source for bicyclists competing in the Tour de France. According to the video, most of the energy content in the food is used by the bicyclists for a) accelerating during occasional sprints. b) riding uphill. c) overcoming friction in the bearings and sprockets of the bikes. d) overcoming wind resistance. e) producing heat. 83

6 15. What is another way to write 6.1 x 10-3? a) b) c) d) 6,100 e) 61, For which of the following objects would the center of mass fall outside of the actual object? a) pencil b) solid rubber ball c) C clamp d) square wooden block e) meter stick 17. What amount of kinetic energy must be given to a ball with an mass of 0.5 kg in order for the ball to rise a vertical distance of 10 meters? Neglect air resistance. a) 5 joules b) 10 joules c) 30 joules d) 35 joules e) 49 joules 18. What happens to the gravitational force between two bodies if the distance between them triples? a) The force becomes three times larger. b) The force doesn't change. c) The force becomes one third as large. d) The force becomes one eighth as large. e) The force becomes one ninth as large. 84

7 19. In the video Why Physics? which of the following is a situation in which the study of physics was NOT discussed? a) changing a flat tire on a car b) parachuting off of a bridge c) launching the Hubble telescope into orbit with the space shuttle d) balancing on ropes during camping activities e) eating cookies in space 20. In class we put drops of water in a hollow drill bit and created friction in order to pop a cork from the end of the bit. Assuming that the cork shot high into the air, what is the sequence of energy transformations starting with the drill and ending with the cork on the floor? a) electrical, mechanical, thermal, mechanical, gravitational, mechanical, thermal b) thermal, mechanical, thermal, electrical, gravitational, mechanical, thermal c) thermal, mechanical, nuclear, mechanical, electrical d) electrical, radiant, thermal, gravitational, mechanical e) electrical, chemical, thermal, mechanical, gravitational, mechanical, radiant 21. If you push a uniform block of wood slowly over the edge of a table, the block will start to fall when a) the block's center of mass moves past the table's center of mass. b) the force of friction equals the force of gravity. c) the block's center of mass moves past the edge of the table. d) the force of friction is twice the force of gravity. e) one third of the block moves past the edge of the table x 10 4 / 8 x 10-2 is between a) 10 1 and 10 2 b) 10 2 and 10 3 c) 10 3 and 10 4 d) 10 5 and 10 6 e) 10 6 and

8 23. A body moving at constant speed in a circle is a) not accelerated. b) not experiencing a net force. c) not changing its velocity. d) accelerating. e) not obeying Newton's Second Law. 24. You are given two light bulbs that appear equally bright. How can you tell which one is more efficient? a) The more efficient bulb feels warmer. b) The more efficient bulb feels cooler. c) The more efficient bulb weighs less. d) The more efficient bulb weighs more. e) Since both light bulbs appear equally bright, the efficiency of both light bulbs must be the same. 25. On the planet Xeres, the acceleration of gravity (g) is 4.9 meters/second 2. If a space vehicle weighs 20,000 newtons on earth, how much will it weigh on Xeres? a) 2,041 newtons b) 10,000 newtons c) 20,000 newtons d) 40,000 newtons e) 196,000 newtons 26. Which of the following is NOT an example of a chemical to thermal to mechanical energy of motion (kinetic energy) conversion? a) a coal-burning steam engine moving a train b) a coal-burning power plant turning a turbine c) a burning factory exploding and throwing debris all around it d) a gasoline engine moving a car e) All of the above demonstrate the same energy conversion sequence. 86

9 27. The sail cart demonstrated in class does not move when the sail is attached. The fact that the cart does not move is most easily explained in terms of a) friction. b) conversion of electromagnetic energy into mechanical energy. c) conversion of mass into energy. d) the law of gravitation. e) Newton's Laws of Motion. 28. Which of the following statements is TRUE? a) If one is clever, one can design a machine that will generate more energy than the energy required to operate the machine. b) If one is clever, one can design a machine that will operate with no waste of useful energy. c) There is always some waste of useful energy in the operation of any machine. d) When a light bulb is lit, the radiant energy plus the thermal energy dissipated exceeds the electric energy drawn from the electric outlet. e) None of the above statements are true. 29. Every minute after a chemical is added to a colony of bacteria, the number of bacteria is halved. If the present number of bacteria is 3,000, how many minutes ago was the number 24,000? a) 1 minute b) 2 minutes c) 3 minutes d) 4 minutes e) 8 minutes 30. One light-year is the distance that light travels in a year. One parsec is 3.26 light-years. Use the fact that the speed of light is 186,000 miles per second to determine how many miles are equal to one parsec. a) 6.06 x 10 5 miles b) 2.18 x 10 9 miles c) 5.24 x miles d) 5.86 x miles e) 1.91 x miles 87