Physics: Second Semester Final Exam Review



Physics: Second Semester Final Exam Review

Conservation of Energy

KEY CONCEPT: The total mechanical energy (kinetic + potential) of an object is conserved. Find the total mechanical energy at the beginning, and that will be the total at the end.

1. A hot air balloon is hovering in the air when it drops a 40 Kg food package to some lost golfers. If the package is dropped from an altitude of 500 m and air resistance can be neglected, how fast is the package moving when it hits the ground?

(99.05 m/s)

2. Tyler is sliding down a frictionless 15 m tall hill. He starts at the top with a velocity of 10.0 m/s. What is his velocity at the bottom of the hill? (19.86 m/s)

KEY CONCEPT: The work required to change the speed of an object is equal to the change in kinetic energy of the object. That’s the Work-Energy Theorem. Work = Force x distance.

3. At the end of the Shock Wave roller coaster ride, the 6000-kg train of cars (includes passengers) is slowed from a speed of 20 m/s to a speed of 5 m/s over a distance of 20 meters. Determine the braking force required to slow the train of cars by this amount. (-56250 N)

Momentum and Impulse

KEY CONCEPT: Total momentum is conserved. Force x time = Impulse. Impulse = Change in Momentum.

1. A person on roller blades with a mass of 70 kg throws a ball with a mass of 15 kg. The person throws the ball with a speed of 5.0 m/s. What is the speed of the person after the ball is thrown? (-1.07 m/s)

2. A brake with a force of 20 Newtons is applied for 10 seconds to stop a 20 kilogram model car moving at 30 meters per second. What is the magnitude of the impulse to stop the car? (200 N s)

3. A sticky ball that has a mass of 3 kg is thrown with a velocity of 8m/s at a stationary cart that has a mass of 10 kg. If the ball sticks to the side of the cart, what is the momentum of the two objects moving together? (1.85 m/s)

Simple Machines

KEY CONCEPT: Work input is the work done by the user of the machine. Work output is the work accomplished. The work output is always less than the work input.

1. You are using a lever to lift the edge of a heavy rock in order to slide a roller under it. The rock weighs 5,500 N. You are able to exert a force of 430 N and move the handle of the lever 1.50 meters. The rock lifts a distance of 0.0900 meters.

A) What are the input and output work done? (Win = 645 J, Wout = 496 J)

B) What is the mechanical advantage of the lever? (MA = 12.79)

2. A worker pushes a 50.0-kg cylinder up a frictionless incline at constant speed to a height of 3-meters. A diagram of the situation is shown at right.

How much work is done lifting the cylinder up the 3.0m height? (1471.5 J)

How much force is required to push the cylinder up the incline? (245.25 N)

How much force would be required to lift the cylinder without the ramp? (490.5 N)

What is the mechanical advantage of the ramp? (2)

Circular Motion

KEY CONCEPT: Objects tend to go in a straight line. If an object is moving in a circle, there must be a centripetal force in the direction of the center of the circle.

1. Which of the following statements are true of an object moving in a circle at a constant speed? Include all that apply.

a. The object experiences a force which has a component directed parallel to the direction of motion.

b. Inertia causes objects to move in a circle.

c. Because the speed is constant, the acceleration is zero.

d. The acceleration and the net force vector are directed perpendicular to each other.

e. If the net force acting upon the object is suddenly reduced to zero, then the object would suddenly depart from its circular path and travel tangent to the circle.

f. The acceleration of the object is directed tangent to the circle.

2. A race car travels around a flat, horizontal, circular track with a radius of 50.0 meters. The mass of the race car is 400 kg. The maximum centripetal force the track can exert on the tires of the race car is 2400N. What is the maximum speed the race car can go without sliding off the track? (17.32 N)

3. A 0.200-kg object is tied to the end of a cord and whirled in a horizontal circle of radius 1.20 meters at a constant 3.0 revolutions/second. Find the acceleration of the object and the tension in the cord. (Hint: The tension in the cord is the source of the centripetal force.) (ac = 426.37 m/s2, F = 85.27 N)

Electrostatics

1. Which of the following are true of static charges? Choose all that apply.

a. Like charges repel.

b. Opposite charges repel.

c. A positively charged object has lost electrons.

d. A positively charged object has gained protons.

e. A negatively charged object has lost protons.

f. A negatively charged object has gained electrons.

2. Identify the type of charge on objects A-B based on the electric field lines shown for each configuration of charges. Your choices in each case are: positive, negative, neutral.

[pic] [pic]

A _____Positive____________ B ______Negative________________

3. Indicate the final charge on the sphere in each scenario. Your choices are positive, negative, or neutral.

[pic]

a. A positively charged balloon is touched to a neutral conducting sphere, and then the balloon is removed. (Positive)

[pic]

b. A positively-charged balloon is held near a neutral conducting sphere. The sphere is then touched on the opposite side. (Negative)

[pic]

c. A negatively-charged rod is held near a neutral conducting sphere. The sphere is touched on the opposite side. (Positive)

Electric Circuits

1. Find the voltage drop and current through each resistor in the diagram above.

[pic]

2. Find the voltage drop and current through each resistor in the diagram above.

Heat

1. Define conduction, convection, and radiation, and give two examples of each.

a. conduction _______Transfer of heat via direct contact.___________ _______________

___________________________________________________________________________

b. convection ________ Transfer of heat via currents (in fluids). ____________________

___________________________________________________________________________

c.radiation___________ Transfer of heat via electromagnetic waves.________________________

____________________________________________________________________________

2. How many grams of water would require 2.20 x 104 joules of heat to raise its temperature from 34.0°C to 100.0°C? The specific heat of water is 4.18 J/g∙°C. (79.74g)

3. If 200. grams of water is to be heated from 24.0°C to 100.0°C to make a cup of tea, how much heat must be added? The specific heat of water is 4.18 J/g∙°C (63536 J)

Waves , Sound and Light Practice Questions:

1. If the particles of the medium are vibrating to and fro in the same direction of energy transport, then the wave is a ____ wave.

|a. longitudinal |b. sound |c. standing |d. transverse |

2. When the particles of a medium are vibrating at right angles to the direction of energy transport, then the wave is a ____ wave.

|a. longitudinal |b. sound |c. standing |d. transverse |

3. If the energy in a longitudinal wave travels from south to north, the particles of the medium would be vibrating _____.

|a. from north to south, only |b. both north and south |

|c. from east to west, only |d. both east and west |

4. The main factor which affects the speed of a sound wave is the ____.

|a. amplitude of the sound wave |b. intensity of the sound |

|c. loudness of the sound |d. properties of the medium |

5. What is the amplitude of the wave in the diagram below?

[pic]

|a. 0.03 m. |b. 0.04 m. |c. 0.05 m. |d. 0.06 m. |

6. The wavelength of the wave in the diagram above is ____ m.

|a. 0.030 |b. 0.040 |c. 0.060 |d. 0.080 |

7. Why does sound diffract more than light does?

|a. |Because sound comes in many frequencies. |

|b. |Because sound has a longer wavelength. |

|c. |Because sound is a longitudinal wave. |

|d. |Because sound has a greater amplitude. |

8. How many complete waves are shown in the diagram above?

|a. 1 |b. 2 |c. 3 |d. 1.5 |

9. A musical tone sounded on a piano has a frequency of 410 Hz and a wavelength of 0.80 m. What is the speed of the sound wave?

|a. |170 m/s |c. |330 m/s |

|b. |240 m/s |d. |590 m/s |

10. If you hear the pitch of a siren become lower, you know that

|a. |neither you nor the siren is moving. |

|b. |you are moving toward the siren or the siren is moving toward you. |

|c. |you are moving away from the siren or the siren is moving toward you. |

|d. |the source has just passed you or it is accelerating away from you. |

11. Draw a diagram to illustrate each wave phenomenon:

a. diffraction b. interference c. reflection

Bending of a wave addition / subtraction of bouncing of a wave off of a

around a barrier wave amplitudes boundary or barrier

d. refraction e. resonance

Bending of a wave in forced vibration at an objects natural frequency

a new medium.

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V2Ω = 4V

V20Ω = 8V

V10Ω = 8V

V10Ω = 8V

I2Ω = 2A

I20Ω = .4A

I10Ω = .8A

I10Ω = .8A

V2Ω = 6V

V4Ω = 6V

V糊糌紪紬紮絀絔絨絼絾綐綦綼緒緔緖緘線緬緾萐萤萦萸葎葠葶葸葺ýffýﴀýﴀööööö6Ω = 6V

V10Ω = 6V

I2Ω = 3A

I4Ω = 1.5A

I6Ω = 1A

I10Ω = .6A

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