Physics 207 Exam #1
Spring 2005
Name:______
1) What is the general relationship between per capita income and per capita energy use for the nations of the world? (4 points)
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2) What are the three basic energy use sectors in the United States? (2 points each)
a) ______
b) ______
c) ______
3) Approximately what percentage of the United States energy comes from fossil fuels? (3 points)
4) According to the Hubert Model which figure shown below best represents the production of a natural resource as a function of time? ______(3 points)
5) What is meant by a PROVEN RESERVE of a natural resource? (3 points)
______
______
______
6) What is meant by an UNPROVEN RESERVE of a natural resource?(3 points)
______
______
______
7) Between 1950 and 1970, the US energy use increased at approximately 4.5% per year. In 1950 we used 30 Quadrillion BTU of energy. How many years did it take for the energy use to increase to 60 Quadrillion BTU? (4 points)
8) The book makes the comment that “conservation may be our best new energy resource.” List three advantages to implementing conservation technologies. (the book actually lists six) (1 points each)
a) ______
b) ______
c) ______
9) Indicate whether the quantities listed below are examples of scalars or vectors. (1 points each)
a) Acceleration ______
b) Temperature ______
c) Volume ______
d) Force ______
e) Velocity ______
f) Mass ______
g) Momentum ______
10) Given that 5280 ft = 1 mi, 1 ft = 12 in and 3600 s = 1hr, what would a speed of 65 mi/hr be in terms of inches per second? (4 points)
11) A 2 kg rock is dropped off of a high cliff and takes 5 seconds to reach the bottom. (Assume that we may neglect air drag and that the acceleration due to gravity is downward with a magnitude of 9.8 m/s2.)
a) How high is the cliff? (4 points)
b) How fast is the rock moving when it hits the ground? (4 points)
c) What is the kinetic energy of the rock when it hits the ground?(4 points)
12) A 400 kg cannon shoots a 5 kg cannon ball. If the cannon recoils to the left with a speed of 5 m/s, what is the velocity (magnitude and direction) of the cannon ball? (4 points)
13) How much work is done in lifting a 100 kg object a distance of 3 m in the earth’s gravitational field? (4 points)
14) Consider the heat engine shown. In each cycle
Of operation the engine takes in 1000 J of
energy from a hot reservoir at 900 K and
performs 400 J of work and puts the remaining
energy into a cold reservoir at 300 K.
a) What is the efficiency of this heat engine?
(4 points)
b) What is the efficiency of the best possible eat engine operating between these two temperature reservoirs? (4 points)
15) Given that the specific heat of silver is 0.056 cal/g°C, how much heat energy must we add to 100 g of silver to raise its temperature by 15°C? (4 points)
16) The highest temperature ever recorded in Death Valley CA is 54.7g°C. What is this in degrees Fahrenheit? (4points)
17) Briefly explain why the second law of thermodynamics is true, i.e. why can’t you have a heat engine that is 100% efficient. (3 points)
Multiple Choice (3 points each)
18___ / What can be said about an object that is moving in a straight line with a constant speed?a) There is no net force on the object.
b) The object has zero acceleration.
c) The object is moving with constant velocity.
d)All of the above.
e) None of the above.
19___ / Even though only a little over 4% of the worlds population lives in the United States, we represent approximately of the worlds energy use.
a) 5 %
b) 10 %
c) 24%
d) 43%
20___ / What are the four fundamental forces in nature?
a) fossil, solar, wind, hydroelectric
b) gravity, electromagnetism, weak nuclear, strong nuclear
c) radiation, conduction, convection, ablation
d) Army, Navy, Air Force, Marines
21___ / Which of the heat transfer mechanisms occurs primarily in solids?
a) convection
b) conduction
c) radiation
d) insolation
22___ / Which of the heat transfer mechanisms is responsible for transferring the sun’s energy to the earth?
a) convection
b) conduction
c) radiation
d) insolation
23___ / Two objects each have the same net force applied to them. If object 1 has twice the mass of object 2, which of the following statements are correct?
a) Object 1 will have twice the acceleration of object 2
b) Object 1 and object 2 will have the same acceleration
c) Object 1 will have half the acceleration of object 2
d) None of the above.
24 __ / Water has a much larger specific heat than iron. If equal amounts of heat are added to equal masses of water and iron, which of the following is true?
a) The water will have a larger temperature change than the iron.
b) The water will have a smaller temperature change than the iron.
c) Since equal amounts of heat are added to equal masses, the temperature change will be the same for each.
Potentially Use Equation
Doubling time/ Thermal Energy
Newton’s 2nd Law
/ If we know Fahrenheit and want Celsius
Definition of momentum
/ If we know Celsius and want Fahrenheit
Kinetic Energy
/ If we know Celsius and want Kelvin
Gravitational Potential Energy
/ Conservation of Energy
If constant acceleration
Heat Engine