PHY Final Exam Review

A .02 kg piece of space junk is travelling at 100 m/s. What is its kinetic energy? (Assume it is not rotating) Note: 𝐾𝐸 = 1/2 𝑚𝑣^2 A. 100 J B. 200 J C. 1000 J D. 2000 J E. Not enough information

A. 100 J Solution: 𝐾𝐸 = 1/2 𝑚𝑣^2 𝑚 = .02 𝑘𝑔 𝑣 = 100 𝑚/𝑠 𝐾𝐸 = 1/2 (.02) (100)^ 2 = (.01) (10 ,000) = 100J

If I lift an object up 6 ft above the ground and hold it still so that it has12 J of potential energy then I drop it. How much kinetic energy does it have just before it hits the ground? Hint: 𝑇𝑜𝑡𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 = 𝑘𝑖𝑛𝑒𝑡𝑖𝑐 𝑒𝑛𝑒𝑟𝑔𝑦 + 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑒𝑛𝑒𝑟𝑔y A. 12 J B. 24 J C. 0 J D. Not enough information E. None of the above

A. 12 J

The temperature outside is 40oF what is it in degrees centigrade? A. 4 C B. 3 C C. 6 C D. 33.5 C E. 67 C

A. 4 C Solution: 𝐶 = (𝐹 − 32)/2 𝐶 = (40 − 32)/2 𝐶 = 4

If a gas in an engine is heated from 300 K to 3000 K in order to move a piston in a cycle and do work what is the efficiency of the engine? Hint: 𝐸 = (1 − 𝑇𝑐/𝑇𝐻) × 100% A. 90% B. 10% C. 190% D. 19%

A. 90% Solution: 𝐸 = (1 − 𝑇𝑐/𝑇ℎ) × 100% 𝐸 = (1 − 300/3000) × 100% 𝐸 = (1 − .1) × 100% 𝐸 = 90%

Cars A and B are racing. Car A is half as heavy as car B but is moving twice as fast as car B. Which car has more kinetic energy? Hint: 𝐾𝐸 = 1/2 𝑚𝑣^2 A. Car A B. Car B C. Both cars have the same amount of kinetic energy D. Not enough information

A. Car A Solution: 𝐶𝑎𝑟 𝐴: 𝐾𝐸 = 1/2 𝑚 /2 (2𝑣)^2 = 𝑚𝑣 2 𝐶𝑎𝑟 𝐵: 𝐾𝐸 = 1/2 𝑚𝑣^2 Car A has twice as much kinetic energy as car B

A Calorie (C) is a unit of measure for what quantity? A. Energy B. Power C. Weight D. Mass E. Nutrition

A. Energy

You have been told that for an ideal gas the speed of sound depends only on the temperature of the gas. What will happen to the speed of sound in the gas if you increase the volume of a gas in an expandable container at constant pressure? Hint: 𝑃𝑉/𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. It will increase B. It will decrease C. It will stay the same' D. I don't have a clue

A. It will increase Solution: If the volume increases at constant pressure the temperature must increase by the same amount.

You have been told that for an ideal gas the speed of sound depends only on the temperature of the gas. What will happen to the speed of sound in the gas if you increase the pressure of a gas in a cylinder of constant volume? Hint: 𝑃𝑉/𝑇 = 𝐶 A. It will increase B. It will decrease C. It will stay the same' D. I don't have a clue

A. It will increase Solution: If you increase the pressure at constant volume, then the temperature must increase. If the temperature increases the speed of sound must increase

If a sound wave travels from a layer of warm air into a layer of colder air, what will happen to its speed? A. It will slow down B. It will speed up C. It will not change D. Not enough information E. Haven't got a clue

A. It will slow down Solution: The speed of sound is the speed of the molecules in the gas. It the temperature of the gas is increased the kinetic energy of the gas is increased Therefore the speed of the molecules must increase

Which of the following is referred to as energy of motion. A. Kinetic energy B. Potential energy C. Coal energy D. Nuclear energy E. None of the abo

A. Kinetic energy

If I lift an object off the ground 4 m and hold it there, have I increased its potential energy relative to when it was sitting on the ground. A. Yes B. No C. It depends upon how fast you lift it D. Not enough information

A. Yes

For many years the U.S. has been heavily dependent on imported oil and gas for much of its energy needs. However in the past ten years we have significantly increased our oil and natural gas production. Has this increase been sufficient to allow us to export either of these. A. Yes B. No C. I don't know

A. Yes

The speed of sound in an ideal gas depends primarily upon..... A. The temperature of the gas B. The volume of the gas containing the gas C. The pressure of the gas D. None of the above E. No clue

A. The temperature of the gas

A cold glass of juice and a hot cup of coffee are sitting on a wooden table in a dining room. The juice and the coffee are about 3 feet apart. If they are not disturbed they will eventually reach thermal equilibrium. A. True B. False

A. True

Sound always requires some medium (that is some material made up of atoms) to be transmitted. A. True B. False

A. True

The kinetic energy of a molecule in an ideal gas is proportional to the temperature of the gas. A. True B. False

A. True

We are using less coal today than we did 20years ago A.True B.False

A. True

In principle it should be possible for us to develop a device that will allow us to cool a gas to absolute zero. A. True B. False

A. True The Second Law of Thermodynamics tells us we cannot take all the heat energy out of a gas. We must always exhaust some heat to the environment.

How much do I have to increase the temperature of an ideal gas to double its energy? 𝐻𝑖𝑛𝑡:𝐾𝐸 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 × 𝑇 A. Twice B. Four times C. Eight times D. Not enough information

A. Twice 𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛: 2 × 𝐾𝐸 = 2 × T

According to the graph, if you spend most of your time driving between 20 mph and 60 mph for which car would you spend less on fuel? (graph shows Car A (blue) starting a zero with an arch, Car B (red) shows a line starting a 25 going down like this \) A. Vehicle A B. Vehicle B C. Not enough information

A. Vehicle A

Based on the graph below which vehicle gets better mileage at 60 Mph? (graph shows Car A (blue) starting a zero with an arch, Car B (red) shows a line starting a 25 going down like this \) A. Vehicle A B. Vehicle B C. Not enough Information

A. Vehicle A

Does the equivalent of the bow wave concept apply to automobiles? A. Yes B. No

A. Yes

If I boil water in a container and allow the pressure to build up until the container bursts do I have an explosion? A. Yes B. No

A. Yes Solution: • Any very rapid release of energy can be an explosion is does not have to be a chemical or nuclear reaction.

Suppose I have two rooms filled with an ideal gas at the same temperature, that means the molecules in them have the same average kinetic energy. If one room has fewer molecules in it Is the speed of sound the same in both rooms? A. Yes B. No

A. Yes • The speed of sound is the speed of the molecules. • The speed of the molecules depends only on the mass of the molecules and their kinetic energy. • Their kinetic energy depends only on the temperature. • Therefore since the mass of each of the molecules in both rooms is the same • The number of molecules does not affect their speed. • Their speed depends only on the temperature

What is the kinetic energy of a bullet with a mass of .05 kg travelling at 800 m/s? Hint: 𝐾𝐸 = 1/2 𝑚𝑣^2 A. 32,000 J B. 16,000J C. 40 J D. 20 J

B. 16,000J

Poppa John's sells two 9" pizzas for $9 and one 18" pizza for $16. If you love pizza which one is the better deal? Hint: 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑎 𝑐𝑖𝑟𝑐𝑙𝑒 𝑖𝑠 𝜋𝑟^2 A. Two for $9 B. 1 for $16 C. They are the same because the 18" pizza is twice as big as one 9" pizza D. Not enough information

B. 1 for $16

If you heat a gas in an engine to 1000 C causing a piston to exert a constant force of 50 N on a piston which moves a mass 2 m and then cool the gas to 100 C causing the piston to release the mass and retract without moving the mass, how much work has the piston done on the mass? A. 50 J B. 100 J C. 900 J D. 1000 J

B. 100 J w𝑜𝑟𝑘 = 𝑓𝑜𝑟𝑐𝑒 × 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑜𝑟𝑐𝑒 = 50𝑁 𝑑𝑖𝑠𝑡𝑛𝑐𝑒 = 2 𝑚 𝑤𝑜𝑟𝑘 = 50𝑁 × 2𝑚 𝑊𝑜𝑟𝑘 = 100 𝐽 𝑇ℎ𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒𝑠 𝑤𝑖𝑙𝑙 𝑎𝑙𝑙𝑜𝑤 𝑦𝑜𝑢 𝑡𝑜 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒 𝑡ℎ𝑒 𝑒𝑓𝑓𝑒𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑒𝑛𝑔𝑖𝑛𝑒, 𝑏𝑢𝑡 𝑡ℎ𝑒 𝑤𝑜𝑟𝑘 𝑜𝑛 𝑡ℎ𝑒 𝑚𝑎𝑠𝑠 𝑖𝑠 𝑡ℎ𝑒 𝑡𝑜𝑡𝑎𝑙 𝑓𝑜𝑟𝑐𝑒 𝑡𝑖𝑚𝑒𝑠 𝑡ℎ𝑒 𝑡𝑜𝑡𝑎𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡ℎ𝑒 𝑚𝑎𝑠𝑠 𝑖𝑠 𝑚𝑜𝑣𝑒𝑑.

Assume one pound provides approximately 3600 Calories and a person burns 2300 Calories a day. If that person wants to loose 1 lb. every 6 days how many Calories should they consume each day? A. 600 C B. 1700 C C. 2900 C D. 2000 C

B. 1700 C Solution: • If the person needs to eat a total of 3600 calories less in 6 days then they need to eat 3600/6 = 600 fewer calories each day. • The number of calories the need to consume to loose weight is 2300 − 600 = 1700 calories.

A ball has 7 J of kinetic energy and 14 J of potential energy when it is 2 meters above the ground. How much energy will it have just before it hits the ground. A. 7 J B. 21 J C. 14 J D. 2 J E. Not enough information

B. 21 J Solution: Energy is conserved so the total energy remains the same. 7𝐽 + 14𝐽 = 21𝐽 The potential energy will be converted to kinetic energy but the total energy will remain the same.

Assume a 1 m2 solar panel will generate 400 W of electric power. How long does the sun have to shine on the panel to generate 1600 Joules of energy. (1 W = 1 Joule/sec) A. 4 hours B. 4 seconds C. 1000 seconds D. 40 seconds

B. 4 seconds Solution: • 1 panel generates 400 W • 1 Joule = 1 W x 1 sec • I need 1600 Joules • (400 W) X ( t sec) = 1600 W sec • t sec = (1600 W sec)/(400 W) = 4 sec

Assume a solar panel 1 m^2 can generate 400 W. If 1 horsepower is 800 W, how large does a solar array have to be to generate 200 hp? A. 200 m^2 B. 400 m^2 C. 4000 m^2 D. 1600 m^2

B. 400 m^2

If power is defined as a quantity of energy divided by the amount of time it is used and a unit of energy is a kilowatt-hour, from this information what would you conclude to be a unit of power? Power = Energy used/Time it was used A.An hour B.A kilowatt C.A kilowatt-hour per second squared D.An hour per kilowat

B. A kilowatt

Which engine is more efficient? Engine A absorbs heat at 6000 K and exhausts it at 600 K and engine B absorbs heat at 600 K and exhausts it at 6 K A. Engine A B. Engine B C. They are equally efficient D. None of the above E. Not enough information

B. Engine B Solution: 𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛: 𝐸 = (1 − 𝑇𝑐/𝑇ℎ) × 100% 𝐸𝐴 = (1 − 600/6000) × 100% 𝐸𝐴 = (1 − .1) × 100% 𝐸𝐴 = 90% 𝐸𝐵 = (1 − 6/600) × 100% 𝐸𝐵 = (1 −.01) × 100% 𝐸𝐴 = 99%

Which engine is more efficient? Engine A starts at 250 C and exhausts gas at 50 C Engine B starts at 5000 C and exhausts gas at 500 C Hint: 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = (1 − 𝑇𝑐𝑜𝑙𝑑 𝑇ℎ𝑜𝑡 ) × 100% A. Engine A B. Engine B C. Both engines are equally efficient D. None of the above E. Help!

B. Engine B 𝐸𝐴 = (1 − 50/250) × 100% = (1 − .2) × 100% = 80% 𝐸𝐵 = (1 − 500/5000) × 100% = (1 − .1) × 100% = 90%

Suppose I have a disk with a hole in it and I heat it up...what happens?

B. Expands, gets bigger

Based on the discussion in class a major barrier to the use of hydrogen for automobiles is how to store it in the vehicle. A. True B. False

B. False

Celsius or Centigrade thermometer measures a different kind of temperature than the one measured by a Fahrenheit thermometer. A. True B. False

B. False

The primary reason the hydrogen fuel cell is not used to generate electricity is the amount of pollution it creates. A. True B. False

B. False

The wind could be a significant source or renewable energy for the U.S. but unfortunately there are very few places where the wind blows most of the time. As a result the total amount of power generated in the U.S, by wind turbines is not likely to contribute significantly to our total energy needs. A. True B. False

B. False

There are 3 types of energy: kinetic energy, potential energy and heat energy. A. True B. False

B. False

Wind energy is not widely used because the wind does not blow consistently in any one spot. A. True B. False

B. False

Energy is almost always conserved but under very rare conditions energy conservation is not true. A. True B. False

B. False Energy is always, always conserved. It can be neither created or destroyed.

If two objects are in a vacuum and one of them is heated to red hot no heat will be transmitted to the other object. A. True B. False

B. False False. There are three ways heat is transmitted: • Conduction • Convection • Radiation (Electromagnetic) The first two require a molecular motion so molecules must be present. Radiation does not require any medium.

As discussed in lecture, there are really three types of energy: kinetic energy, potential energy, and heat energy. A. True B. False

B. False There are on 2 types of energy: kinetic and potential. Heat is kinetic energy

Which of the following has the greatest amount of energy per unit weight? A. Gasoline B. Hydrogen C. Coal D. Natural Gas

B. Hydrogen

If I increase the frequency 𝑓 of a sound wave what happens to the wavelength 𝑙 of the sound? Assume the speed of sound does not change with frequency. Hint: Frequency is the number of waves per second. Wavelength is the distance between when a wave starts and when it finishes. A. It increases B. It decreases C. It remains the same D. Not enough information

B. It decreases

If I double the volume of a balloon keeping the pressure constant, what happens to the temperature? Hint: 𝑃𝑉/𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. It remains the same B. It doubles C. It increases four times D. Not enough information

B. It doubles Solution: 𝑃𝑉/𝑇 = 𝑃′𝑉′/𝑇′ 𝑃 = 𝑃′ 2𝑉 = 𝑉′ 𝑇 =? 𝑃𝑉/𝑇 = 𝑃2𝑉/𝑇′ 𝑇 ′ = 2T

If I double the temperature of an ideal gas, how much has the energy of the gas increased due to molecular motion? Hint: 𝑇 ∝ 𝐾𝐸 A. It doesn't change B. It has doubled C. It is 4 times as great D. Not enough information E. I don't have clue

B. It has doubled Solution: 2 × 𝑇 ∝ 2 × 𝐾E

Suppose I double the pressure of a gas and keep the volume constant, what will happen to the temperature? Hint: 𝑃𝑉 𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. It will stay the same B. It will double C. It will triple D. It will decrease by ½ E. None of the above

B. It will double Solution: 𝑃𝑉/𝑇 = 𝐶 = 𝑃′𝑉′/𝑇′ 𝑃𝑉/𝑇 = 𝑃′𝑉′/𝑇′ 𝑃′ = 2𝑃 𝑉′ = 𝑉 𝑇′ =? 𝑃𝑉/𝑇 = 2𝑃𝑉/𝑇′ 1/𝑇 = 2/𝑇′ 𝑇' = 2T

Suppose I halve the pressure of a gas and keep the temperature constant, what will happen to the volume? A. It will stay the same B. It will double C. It will triple D. It will decrease by ½ E. None of the above

B. It will double Solution: 𝑃𝑉/𝑇 = 𝑃′𝑉′/𝑇′ 𝑃/2 = 𝑃′ 𝑇 = 𝑇′ 𝑉′ =? 𝑃𝑉/𝑇 = 𝑃/2 𝑉′/𝑇 𝑉 ′ = 𝑉/2

We have heard that the product of the pressure of a gas and the volume in which it is contained is proportional to its temperature. 𝑃𝑉 ∝ 𝑇. If I open a valve releasing the pressure of a gas in a cylinder of volume 𝑉 what will happen to the temperature of the gas remaining in the cylinder? A. It will get warmer B. It will get colder C. It won't change D. I don't know how to figure this out

B. It will get colder Solution: 𝑃𝑉 ∝ 𝑇 , 𝐼𝑓 𝑦𝑜𝑢 𝑑𝑒𝑐𝑟𝑒𝑎𝑠𝑒 𝑜𝑛𝑒 𝑠𝑖𝑑𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑒𝑙𝑎𝑡𝑖𝑜𝑛, 𝑡ℎ𝑒 𝑜𝑡ℎ𝑒𝑟 𝑠𝑖𝑑𝑒 ℎ𝑎𝑠 𝑡𝑜 𝑔𝑒𝑡 𝑠𝑚𝑎𝑙𝑙𝑒𝑟. 𝑆𝑜 𝑖𝑓 𝑉𝑔𝑒𝑡𝑠 𝑠𝑚𝑎𝑙𝑙𝑒𝑟 𝑎𝑛𝑑 𝑃 𝑟𝑒𝑚𝑎𝑖𝑛𝑠 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒, 𝑇 𝑚𝑢𝑠𝑡 𝑔𝑒𝑡 𝑠𝑚𝑎𝑙𝑙𝑒r

If a car weighs 2 tons and is moving at 15 mph and I triple its speed to 45 mph by how much will its kinetic energy increase? (Hint: 𝐾𝐸 = 1/2 𝑚𝑣^2) A. It will triple B. It will increase nine times C. It will increase by 27 times. D. Not enough information E. None of the above

B. It will increase nine times • 𝐾𝐸15 = 1/2 (2000) (15^2) = (1000) (225) = 225000 • 𝐾𝐸45 = 1/2 (2000) (45^2) = (1000) (2025) = 2025000 • 𝐾𝐸45/𝐾𝐸15 = 2025000/225000 = 9

Suppose I triple the temperature of an ideal gas but keep the pressure constant, what will happen to the volume? Hint: 𝑃𝑉 𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. It will remain the same B. It will triple C. It will decrease by 3 D. It will double E. Note enough information

B. It will triple Solution: 𝑃𝑉/𝑇 = 𝐶 = 𝑃′𝑉′/𝑇′ 𝑃𝑉/𝑇 = 𝑃′𝑉′/𝑇′ 𝑃′ = 𝑃 𝑇′ = 3𝑇 𝑉 ′ =? 𝑃𝑉/𝑇 = 𝑃𝑉'/3𝑇 𝑉/1 = 𝑉'/3 3𝑉 = 𝑉′

If the speed of sound in room B is twice the speed of sound in room A, which room is warmer? A. Room A B. Room B C. The speed of sound is the same in both rooms D. Not enough information E. No clue

B. Room B Solution: The speed of sound depends on the temperature. If the speed is greater the temperature must be greater.

A metal lid is screwed very tightly onto a glass jar. The lid will expand more than the glass for a given change in temperature. If I put the jar and the lid in hot water what will happen? A. The lid will expand and crack the glass jar B. The lid and the jar will expand but the lid will expand more becoming loose C. The lid and the jar will expand together and it will remain stuck D. Note enough information

B. The lid and the jar will expand but the lid will expand more becoming loose

Which item do you think has more energy, a 10 gm lithium battery containing 4000 J of available energy or a shot of alcohol containing 6 calories? Hint: 1 C = 4200 J A. The lithium battery B. The shot of alcohol C. They are about the same D. Not enough information

B. The shot of alcohol

If I increase the temperature of an idea' gas by 4 how much faster are the gas molecules of mass m moving compared to before they were heated? Hint: T ∝ 1 2 𝑚𝑣 2 𝑜𝑟 𝑇 = 𝐶 (1/2 𝑚𝑣^2) 𝑤ℎ𝑒𝑟𝑒 𝐶 𝑖𝑠 𝑎 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. Just as fast, they are the same molecules B. Twice as fast C. Four times as fast D. Six times as fast

B. Twice as fast Solution: 𝑇 = 𝐶 (1/2 𝑚𝑣^2) 𝑣 = square root of 2𝑇/𝐶𝑚 𝑇 ′ = 4𝑇 𝑣′ = square root of 2(4𝑇)/𝐶𝑚 𝑣′ = 2 square root of 2T/𝐶𝑚 𝑣′ = 2v

In the discussion on fuel cells in class we learned fuel cell technology is scalable. In this case what did this mean? A. We can make a cell in different sizes depending upon how much energy we need. B. We can generate a much energy as we need by stacking single cells together like batteries in a flashlight C. Fuel cells can be weighed with a scale D. I don't remember

B. We can generate a much energy as we need by stacking single cells together like batteries in a flashlight

If I exert a force 𝑓 of 6 N on a object in the direction it move, moving it a distance 𝑑 of 3 m how much work 𝑤 have I done? Hint: 𝑤 = 𝑓 × 𝑑 A. 6J B. 3 J C. 18 J D. 2 J E. Help!

C. 18 J Solution: 𝑤 = 𝑓 × 𝑑 𝑤 = 6𝑁 × 3𝑚 𝑤 = 18 J

𝐼𝑓 𝑊 = 80𝑙𝑏𝑠, 𝐷𝐹𝑜𝑟𝑐𝑒= 8𝑓𝑡, 𝑎𝑛𝑑𝐷𝑊𝑒𝑖𝑔ℎ𝑡= 2 𝑓𝑡 𝑤ℎ𝑎𝑡 𝑚𝑢𝑠𝑡 𝐹 𝑏𝑒 𝑡𝑜 𝑗𝑢𝑠𝑡 𝑙𝑖𝑓𝑡 𝑡ℎ𝑒 𝑊? A. 2 lbs. B. 8 lbs. C. 20 lbs. D. 40 lbs. E. None of the above

C. 20 lbs. Solution: 𝐹 × 𝐷𝐹𝑜𝑟𝑐𝑒 = 𝑊 × 𝐷𝑊𝑒𝑖𝑔ℎ𝑡 𝐹 × 8 𝑓𝑡 = 80 𝑙𝑏𝑠 × 2𝑓𝑡 𝐹 = 80 𝑙𝑏𝑠 × 2𝑓𝑡/8 𝑓𝑡 𝐹 = 20 𝑙𝑏s

If the temperature is -6 o F what is it in degrees centigrade (Celsius)? A. -6 C B. -12 C C. -19 C D. -38 C E. Help

C. -19 C Solution: (𝐹 − 32)/2 = 𝐶 (−6 − 32)/2 = −19

If a piece of space junk that weighs .02 kg is traveling toward the International Space Station at 100 m/s we learned in a previous example it has 100 J of kinetic energy relative to the space station. Suppose it hits the space station loosing all of its kinetic energy in .01 seconds, how much power has it generated? A. 100 W B. 20,000 W C. 10 KW D. 5 KW E. 50 K W

C. 10 KW Solution: • 𝑃𝑜𝑤𝑒𝑟 = 𝐸𝑛𝑒𝑟𝑔𝑦 𝑢𝑠𝑒𝑑/ 𝑡𝑖𝑚𝑒 𝑖𝑡 𝑡𝑜𝑜𝑘 𝑡𝑜 𝑢𝑠𝑒 𝑖𝑡 • 𝐸𝑛𝑒𝑟𝑔𝑦 𝑢𝑠𝑒𝑑 = 100𝐽 • 𝑇𝑖𝑚𝑒 𝑖𝑡 𝑡𝑜𝑜𝑘 𝑡𝑜 𝑢𝑠𝑒 𝑖𝑡 = .01𝑠 • 𝑃𝑜𝑤𝑒𝑟 = 100𝐽/.01𝑠 = 10 ,000 𝐽𝑠 • 1 𝐽/𝑠 = 1𝑊 • 1000𝑊 = 1 𝐾𝑊 • 𝑃𝑜𝑤𝑒𝑟 = 10 𝐾W

In the diagram, if the weight is 400 N, what is the tension "T" in the rope. There are 4 sections of rope between the top and bottom pulley sheaves. A. 400 N B. 1600 N C. 100 N D. Not enough information

C. 100 N Solution: Weight = 400lbs • 4 ropes hold the weight • Tension in each rope = 400/4 = 100

Suppose I start with 20 J of potential energy and I convert some of it to 7 J of kinetic energy. How much potential energy do I have left? Hint: Energy is conserved A. 27 J B. 20 J C. 13 J D. 7 J

C. 13 J Solution: Total Energy is conserved Total energy = kinetic energy + potential energy Initially all the energy is potential energy so Total energy = 20 J Later 20 J of Total energy = Potential energy plus 7J of kinetic energy. Therefore 20 J - 7J =13 J of potential energy

1 C is the amount of energy required to raise 1 Kg of water 1 Centigrade. If I incinerate a material in a calorimeter raising 1 Kg of water 5o Centigrade in 7 seconds how much power have I generated? Assume 1C is 4200 Joules. Hint: 𝑃𝑜𝑤𝑒𝑟 = 𝐸𝑛𝑒𝑟𝑔𝑦 𝑢𝑠𝑒𝑑/𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡𝑖𝑚𝑒 𝑡ℎ𝑒 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑠 𝑢𝑠𝑒𝑑 𝑡ℎ𝑒𝑛 𝑐𝑜𝑛𝑣𝑒𝑟𝑡 𝐶 𝑡𝑜 𝐽𝑜𝑢𝑙𝑒s A. 300 Joule/sec B. 6000 Joule/sec C. 3000 Joule/sec D. Not enough information

C. 3000 Joule/sec Solution: • 1 C will raise 1 kg of water 1 degree centigrade • The temperature of 1 kg of water rose 5 degrees centigrade • It took 7 seconds to raise the temperature • Power is Energy/time • 1 C = 4200 J • I used 5 calories in 7 seconds • Power generated = (5 C X 4200 J/C)/(7 sec) = • (5 X 600) J/sec = 3000 J/sec

Assume I can burn 500 C if I exercise for one hour. If 1 watt hour is about 1 C, How large a light bulb could I keep lit for one hour? A. 5 Watt bulb B. 50 Watt bulb C. 500 Watt bulb D. Not enough information

C. 500 Watt bulb Solution: 𝐸𝑛𝑒𝑟𝑔𝑦 𝑢𝑠𝑒 𝑖𝑛 𝑊 = 500𝐶 × 1 𝑊ℎ/𝐶 = 500𝑊ℎ 𝑃𝑜𝑤𝑒𝑟 𝑢𝑠𝑒𝑑 𝑖𝑛 1 ℎ = 500𝑊ℎ/1ℎ = 500W

Its 12 C in Frankfurt, approximately what is the temperature in degrees Fahrenheit? A. −20𝑜𝐹 B. 38𝑜𝐹 C. 56𝑜𝐹 D. 88𝑜𝐹 E. None of the above

C. 56𝑜𝐹 Solution: 𝐹 = 2 × 𝐶 + 32 𝐹 = 2 × 12 + 32 𝐹 = 24 + 32 𝐹 = 56

What is a hydrogen fuel cell? A. A device for storing hydrogen fuel B. A device which burns hydrogen fuel to power an automobile C. A device which uses hydrogen and oxygen to generate electricity D. None of the above

C. A device which uses hydrogen and oxygen to generate electricity

The shock wave from the speed of sound in air is analogous to which of the following? A. The wake of a boat B. The bow wave from a boat C. Both of the above D. None of the above

C. Both of the above

If I double the speed of an object how much does the kinetic energy increase? Hint: 𝐾𝐸 = 1/2 𝑚𝑣^2 A. It remains the same B. It becomes twice as much C. It becomes 4 times as much D. It becomes 8 times as much E. No clue

C. It becomes 4 times as much Solution: 𝐾𝐸 = 1/2 𝑚𝑣^2 If the new speed is 2v, then the new kinetic energy KE ′ is 𝐾𝐸 ′ = 1/2 𝑚 (2𝑣)^ 2 𝐾𝐸 ′ = 1/2 𝑚2^2𝑣^2 𝐾𝐸 ′ = 4 (1/2 𝑚𝑣^2) 𝐾𝐸 ′ = 4𝐾𝐸

𝐾𝐸 = 1/2 𝑚𝑣^2. If I double the speed of an object how much does the kinetic energy increase? A. It remains the same B. It becomes twice as much C. It becomes 4 times as much D. It becomes 8 times as much E. No clue

C. It becomes 4 times as much Solution: • In the beginning • 𝐾𝐸 = 1/2 𝑚𝑣^2 • If I double the velocity the new kinetic energy becomes • 𝐾𝐸 ′ = 1/2 𝑚(2𝑣)^2 • 𝐾𝐸 ′ = 1/2 𝑚4𝑣^2 • 𝐾𝐸 ′ = 4 (1/2𝑚𝑣^2) = 4𝐾𝐸

In addition to lower sales in coal what is another primary reason fewer people are employed in the coal industry. A. Environmental and safety requirements make it harder to find people to do the work. B. People don't want to do that type of work anymore it is manual and dangerous C. Robots and related technologies are replacing people D. Excess government regulation in general.

C. Robots and related technologies are replacing people

I triple the pressure of a gas in a 50 gallon tank from 3 pounds per square inch (psi) to 9 psi. What is the most likely thing to happen to the gas in the tank? 𝐻𝑖𝑛𝑡: 𝑃𝑉/𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. Nothing B. It will get cooler C. It will get warmer D. Not enough information

C. It will get warmer Solution: 𝐼𝑓 𝑃𝑉/𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡, 𝑡ℎ𝑒𝑛 𝑖𝑓 𝑦𝑜𝑢 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑡ℎ𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑤𝑖𝑡ℎ𝑜𝑢𝑡 𝑐ℎ𝑎𝑛𝑔𝑖𝑛𝑔 𝑡ℎ𝑒 𝑣𝑜𝑙𝑢𝑚𝑒, 𝑡ℎ𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑤𝑖𝑙𝑙 ℎ𝑎𝑣𝑒 𝑡𝑜 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑏𝑦 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑎𝑠 𝑡ℎ𝑒 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑖𝑛 𝑡ℎ𝑒 𝑝𝑟𝑒𝑠𝑠𝑠𝑢𝑟𝑒.

If I triple the temperature of an ideal gas and keep the pressure constant what will happen to the volume? Hint: 𝑃𝑉 𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. It will remain the same B. It will double C. It will triple D. Not enough information E. None of the above

C. It will triple Solution: 𝑃𝑉/𝑇 = 𝑃′𝑉′/𝑇′ 𝑃 = 𝑃′ 𝑇 = 3𝑇 𝑉′ =? 𝑃𝑉/𝑇 = 𝑃𝑉′/3𝑇 3𝑉 = V'

One solar cell can generate about ½ a volt of electricity. How many solar cells would you need to connect in series to charge a 12 V laptop battery? A. N=6 B. N=12 C. N=24 D. Not enough information

C. N=24

The total amount of coal sold for all purposes in the United States has declined steadily for the past 7 years. While there are many reasons for this, based on the information presented in class which of the following is most likely the largest contributor. A. Increase in environmental regulations which have increased production costs B. Increase in automation i.e. use of robots and large boring machines C. Significant decrease in the price of natural gas as a result of significant increase in the supply D. Decrease in demand resulting from consumer concern about global warming. E. Other

C. Significant decrease in the price of natural gas as a result of significant increase in the supply

Why are we using less coat today than we did 20 years ago? A. Mining labor costs have driven the price per unit of energy up too much. It is no longer competitive B. Environmental restrictions have driven the price per unit of energy up too much. It is no longer competitive C. The price of natural gas and oil have come down dramatically so that the price per unit of energy is about the same as coal and they are easier to use. D. People don't like coal because it is dirty.

C. The price of natural gas and oil have come down dramatically so that the price per unit of energy is about the same as coal and they are easier to use.

A car is moving with a speed of 30 mph, if I have a car with twice the mass that is going at the same speed (30 mph). What is the kinetic energy of the heavier car compared to the lighter car? (H𝑖𝑛𝑡: 𝐾𝐸 = 1 /2 𝑚𝑣^2) A. ½ as much as the original kinetic energy B. About the same as the original kinetic energy C. Twice as much as the original kinetic energy D. 4 times as much as the original kinetic energy

C. Twice as much as the original kinetic energy Solution: The mass of the first car is m, the mass of the second car is 2m. The Kinetic Energy of the first car is 𝐾𝐸 = 1/2 𝑚𝑣^2 The Kinetic Energy of the second car is 𝐾𝐸 = 1/2 (2𝑚) (𝑣)^ 2 = 2 (1/2𝑚𝑣^2) or 2 times the kinetic energy of the first car

What changed in the last 20 years that made the price of oil and gas competitive with coal? A. More oil and gas were discovered B. It became cheaper to import oil and gas C. We developed a new technology that allowed oil and gas extraction from certain types of rock D. Environmental regulations made coal too expensive

C. We developed a new technology that allowed oil and gas extraction from certain types of rock

Suppose Toby and his friends exert a force of 350 N in the direction the sled moves, pulling it 1000 m. How much work have they done? A. 0.35J B. 350J C. 1000J D. 350,000J

D. 350,000J Solution: • Work = Force(in direction of motion)X Distance • Force = 350 N • Distance = 1000 m • Work = (350 N)(1000m) • Work = 350,000 J • Note: 1 Nm = 1Joule

Two instruments record the sound of an explosion one records the time of the explosion at10:45 PM, the other records it at 10:47 PM. Approximately how far apart are the instruments? (Hint: Sound travels approximately 1 mile in 5 seconds) A. 2/5 of a mile B. 2 miles C. 12 miles D. 24 miles E. Not enough information

D. 24 miles Solution: 10:47-10:45 = 2 minutes = 120 s Sound travels 1 𝑚𝑖𝑙𝑒/5𝑠 The distance = 120𝑠 × 1𝑚𝑖𝑙𝑒/5 𝑠 = 24 𝑚𝑖𝑙𝑒s

If Tommy pushes on a 0.5 square meter plate with a force of 6 N, what is the pressure on the plate? Hint: 𝑃 = 𝑓𝑜𝑟𝑐𝑒 𝑎𝑟𝑒𝑎 A. 0.5 N/m2 B. 6 N/m2 C. 3 N/m2 D. 12 N/m2 E. None of the above

D. 12 N/m2 Solution: 𝑃 = 𝐹𝑜𝑟𝑐𝑒/𝐴𝑟𝑒𝑎 𝐹𝑜𝑟𝑐𝑒 = 6𝑁 𝐴𝑟𝑒𝑎 = .5𝑚^2 𝑃 = 6𝑁/.5𝑚^2 𝑃 = 12 N/𝑚^2

How many degrees Fahrenheit are there between the freezing temperature of water and the boiling temperature of water? A. 100 B. 212 C. 32 D. 180 E. None of the above

D. 180 Solution: Water boils at 212 F and Freezes at 32 F 212 F - 32 F= 180 F

A pendulum has 36 J of energy at the bottom of its swing. How much energy will it have at the top of its swing. Assume the pendulum has a mass of 12 kg and a length of 2 m. Hint: energy is conserved. A. 24 J B. 6 J C. 48 J D. 36 J E. Note enough information

D. 36 J Solution: Energy is conserved so the total amount of energy (potential energy + kinetic energy) must be the same at every point on the path of the swing of the pendulum.

What is meant by the term "hybrid car"? A. A car that can be converted into a truck? B. A car that can run on tracks like train or trolley C. A car that can use either gasoline or diesel fuel D. A car that can use an electric motor sometimes and gasoline motor other times.

D. A car that can use an electric motor sometimes and gasoline motor other times.

Which of the following is one wavelength? A. From A to B B. From C to D C. From E to F D. All of the above E. None of the above

D. All of the above Solution: The wavelength is the distance from where a wave begins to where it begins to repeat itself.

What is (are) the exhaust gas(es) produced by a fuel cell? A. CO and NOx B. CO2 and CO C. CH4 D. H2O E. All of the above

D. H2O

A cylinder contains a gas made up of hydrogen and oxygen in thermal equilibrium. If oxygen molecules are16 times more massive than hydrogen molecules which molecules have a greater average velocity and by how much? Hint: 𝐾𝐸 = 1/2 𝑚𝑣^2 A. Oxygen, 16 times a much B. Oxygen, 4 times as much C. Hydrogen, 16 times as much D. Hydrogen, 4 times as much E. Not enough information

D. Hydrogen, 4 times as much Solution: Since the gases are in thermal equilibrium 𝐾𝐸𝐻𝑦𝑑𝑟𝑜𝑔𝑒𝑛 = 𝐾𝐸𝑜𝑥𝑦𝑔e𝑛 1/2 𝑚ℎ (𝑣ℎ)^2 = 1/2 𝑚𝑜 (𝑣𝑜)^2 𝑚𝑜 = 16𝑚ℎ 1/2 𝑚ℎ (𝑣ℎ)^2 = 1/2 16𝑚ℎ (𝑣𝑜)^2 Canceling like terms (𝑣ℎ)^2 = 16 (𝑣𝑜)^2 Taking the square root of both sides 𝑣ℎ = 4𝑣o

Suppose I have a cubic block of material that is 2" on a side (the length of each side is 2"). If the weight of the block is proportional to its volume, how much more is the weight of a cube of the same material that is 6" on a side? Hint: 𝑉𝑐𝑢𝑏𝑒 = 𝑙^3 A. It remains the same B. It triples C. It becomes 9 times a large D. It becomes 27 times as large E. We need to know the value of 𝜋

D. It becomes 27 times as large Solution: • The weight of the cube is proportional to the volume of the cube. Therefore the change in the weight is proportional to the change in the volume. • The length of each side of the original cube is 2" so its volume is 𝑉𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 = 2^3 = 8cu. In. • The length of each side of the new cube is 6" or 3 times the length of the original side. • 𝑉𝑛𝑒𝑤 = (2 × 3)^3 = 2^3 × 3^3 = 8 × 27 • 𝑉𝑛𝑒𝑤/𝑉𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 = 8×27/8 = 27

Most of the hydrogen we use in the United States comes from.... A. Pockets of hydrogen found underground B. Hydrogen gas extracted from the atmosphere C. Hydrogen produced by nuclear reactors D. It is manufactured from fossil fuels and water

D. It is manufactured from fossil fuels and water

Suppose I halve the pressure of a gas and keep the volume constant, what will happen to the temperature? Hint: 𝑃𝑉 𝑇 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 A. It will stay the same B. It will double C. It will triple D. It will decrease by ½ E. None of the above

D. It will decrease by ½ Solution: 𝑃𝑉/𝑇 = 𝑃′𝑉′/𝑇′ 𝑃/2 = 𝑃′ 𝑉 = 𝑉′ 𝑇 ′ =? 𝑃𝑉/𝑇 = (𝑃/2 𝑉)/𝑇′ 𝑇 ′ = 𝑇/2

Solar energy has a number of advantages, among these the collectors are inexpensive and easy to install. Which of the reasons below is probably the primary reason why local solar collectors are not more widely used to provide electricity to poor communities in underdeveloped countries? A. Lack of sunlight B. No need for electricity C. Distribution D. Storage

D. Storage

Based on the information presented in class which of the following is most responsible for the significant increase in the availability of Natural gas? A. Increase in the price of coal made the price of natural gas more competitive B. More efficient ways to refine petroleum products to produce natural gas C. Recent discoveries of large deposits of natural gas D. The ability to steer a drill in any direction and know where it is

D. The ability to steer a drill in any direction and know where it is

In our first lecture we assumed the cow was a sphere and its weight was proportional to its volume. If we tripled the radius of the sphere how much did its weight increase? Hint:𝑉=4/3 𝜋𝑟^3 A. Three times B. One third times C. Two times D. Twenty seven times E. Nine times

D. Twenty seven times Solution: The initial volume is 4/3 𝜋𝑟^3 . The larger volume is 4/3 𝜋 (3𝑟)^ 3 = 4/3 𝜋 27 (𝑟)^ 3 = 27 (4/3 𝜋𝑟^3) Or 27 times the original volume and therefore the cow is 27 times as heavy.

It is 5 C in Oslo, Norway, What is the temperature in degrees Fahrenheit? A. 5 F B. 32 F C.10 F D.42 F E. Help

D.42 F Solution: (2 × 𝐶) + 32 = 𝐹 (2 × 5) + 32 = 42

If I release .01 J of energy in .0001 seconds how much power have I generated? Hint: Power = 𝑒𝑛𝑒𝑟𝑔𝑦 𝑢𝑠𝑒𝑑/𝑡𝑖𝑚𝑒 𝑖𝑡 𝑡𝑜𝑜𝑘 𝑡𝑜 𝑢𝑠𝑒 𝑖𝑡 A. .000001 W B. .0001 W C. .01 W D. 10 W E. 100 W

E. 100 W

Which of the following is not a unit of energy? A. Calorie B. calorie C. Kilowatt-hour D. Joule E. Kilowatt

E. Kilowatt

According to our text and a past lecture, what are the two types of energy? A. Potential energy and nuclear energy B. Nuclear energy and chemical energy C. Kinetic energy and heat energy D. Heat energy and potential energy E. Kinetic energy and potential energy

E. Kinetic energy and potential energy

What is the speed of sound in a vacuum? A. About 760 ft/s B. About 330 m/s C. About 3x108 m/s D. About 186,000 mi/s E. None of the above

E. None of the above Sound is a vibration wave which requires a medium made up of atoms

A normal flea can jump about 50 times (15 cm) it length (3 mm). Suppose through some genetic experiment a way was found to create a flea with a body diameter 10 times that of a normal flea. If the genetically engineered flea was in scale how far is it likely to be able to jump? A. 15,000 cm B. 1,500 cm C. 150 cm D. 15 cm E. Unlikely to be able to jump.

E. Unlikely to be able to jump.