PHYS 100 Introductory Physics Sample Exam 2

Transcription

1 PHYS 00 Introductory Physics Sample Exam Formulas: Acceleration due to Gravity = 0 m/s Weight = Mass x Acceleration due to Gravity Work = Force x Distance Gravitational Potential Energy = Weight x Height Kinetic Energy = x Mass x (Speed) Work Energy Theorem : Change in kinetic energy equals work done Time Period = Frequency Frequency = Time Period Wave Speed = Wavelength x Frequency Length of string = (# of loops) x Wavelength All questions in this section are mandatory. Choose the one alternative that best completes the statement or answers the question.. A ball is released from the top of a building and it falls without any air-resistance. If it had 400 J of gravitational potential energy at the top, how much kinetic energy will it have just when it hits the ground? a. Exactly 400 J b. More than 400 J c. Less than 400 J d. It depends on the height of the building. Two tuning forks produce a beat frequency of Hz. What are the possible frequencies of the two tuning forks? a. 440 Hz, 0 Hz b. 440 Hz, 44 Hz c. 440 Hz, 880 Hz d. 440 Hz, 330 Hz Page of 5

2 3. The hour hand of a clock undergoes periodic motion. What is the time period of its motion? a. hour b. hours c. minute d. 4 hours 4. Which requires more work: lifting a 50-kg sack vertically meters or lifting a 5-kg sack vertically 4 meters? a. Lifting the 5-kg sack b. Lifting the 50-kg sack c. Amount of work actually depends on the speed with which they are lifted d. Both require the same amount of work 5. Two wave pulses are sent down a rope in opposite directions as shown. Pulse A is 3 cm in height and pulse B is 6 cm in depth. When they overlap, they will create a pulse of B a. 3 cm height b. 3 cm depth c. 9 cm height d. 9 cm depth A 6. You are watching the waves in a lake. You notice that it takes 0 seconds for 5 wave-crests to pass by. What is the frequency of these waves? a. 0 Hz b. 0.5 Hz c. 50 Hz d. 5 Hz 7. An object starting from the same height can take three different paths to reach the ground. For which path will the speed at the bottom be the greatest? You may ignore any friction. a. A b. B c. C d. Speed is the same, irrespective of the path. A B C 8. Which path takes the least amount of time? a. A b. B c. C d. They all take the same amount of time. Page of 5

3 9. As the Earth travels around the Sun the Earth s speed is slowest when the Earth is a. closest to the Sun b. farthest from the Sun c. the Earth s speed is constant d. the Earth s speed is unpredictable 0. A 3 m rope is fixed at both ends and vibrated. What is the wavelength of the fundamental mode of vibration? a..5 m b. 3 m c. 6 m d. 9 m. A car moving at 60 km/hr skids 0 m with locked brakes. How far will the car skid with locked brakes at 90 km/hr? a. 30 m b. 40 m c. 45m d. 60m. Assume that your car has a mass of 000 kg. What is your change in kinetic energy when you decrease the speed of your car from 30 m/s to 0 m/s? a..0 x 0 4 J b. 4.0 x 0 5 J c. 8.0 x 0 5 J d. 9.0 x 0 5 J 3. In the above problem, how much work is done by your breaks? a. +.0 x 0 4 J b x 0 5 J c x 0 5 J d x 0 5 J 4. It takes 600 J to lift an 80 kg couch straight up into the moving truck. How much force would it take to roll the couch up a 4 m long ramp into the same truck? (neglect friction) a. 800 N b. 400 N c. 00 N d. 600 N Standing waves are set up on a string whose total length is 3 m. The pattern looks exactly as it is shown below. Use this diagram to answer question 5 and 6. 3 m Page 3 of 5

4 5. What is the wavelength? a.. m b. 3.0 m c..5 m d..5 m 6. If the frequency of vibration is 60 Hz, what is the speed of the waves whose overlap produces this pattern? a. 7 m/s b. 80 m/s c. 300 m/s d. 50 m/s Use the following to answer questions 7 and 8. A diver who weighs 400 N steps off a diving board that is 0 m above the water. 7. What is the diver s kinetic energy when he hits the water? a. 0 J b. 00 J c. 800 J d J 8. What is the speed with which the diver hits the water. a.0 m/s b. 0 m/s c. 40 m/s d. 400 m/s 9. It takes 40 J of work to push a large box 4 meters across the floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box? a. 60 N b. 40 N c. 4 N d. 0 N 0. Negative work done usually means a. Energy gain b. Energy loss c. No net gain or loss of energy d. Work done is always positive or zero.. An object that has elastic potential energy must be a. stretched like a spring. b. moving. c. at an elevated position. d. at rest. Page 4 of 5

5 . An 80 kg skydiver is falling at a terminal speed of 50 m in second. What power is the skydiver expending on the air? a. kw b. 0 kw c. 4 kw d. 40 kw 3. If you increase your speed from m/s to 6 m/s, how much more kinetic energy do you have? a. 3 times b. 4 times c. 6 times d. 9 times For questions 4 and 5, consider the following waveforms: I II III IV 4. Which one of the above has the smallest amplitude? a. I b. II c. III d. IV 5.Which one of the above has the longest wavelength? a. I b. II c. III d. IV Page 5 of 5