Chapter 3 Energy

An absolute temperature of 100 K is the same as a Celsius temperature of

A. -173°C.

At which of the following Celsius temperatures will a Fahrenheit thermometer show the same reading in degrees?

A. -40°C

A 2-kg book is held 1 m above the floor for 50s. The work done is

A. 0

An ideal frictionless engine takes in 10 kJ of heat per second when it operates between 500 K and 400 K. The work that the engine does per second is

A. 2 kJ.

The pressure on 100 liters of helium is increased from 100 kPa to 400 kPa. The new volume of the helium is

A. 25 liters.

The properties of several different materials are being compared. If the samples all have the same volume, the one with the greatest mass also has the greatest

A. Density

Ice floats in water because

A. its density is less than that of water.

On a molecular level heat is

A. kinetic energy

Six kJ of work is used to lift an object to height of 100 m. The objects approximate mass is

B. 6 kg.

When a liquid becomes a vapor,

C. it must absorb heat.

If a shell fired from a cannon explodes in midair,

C. its total KE increases

An object that has linear momentum must also have

C. kinetic energy

In order for an object to sink when placed in water, the object's average density must be

C. more than that of water.

Of the following, a molecule is best described as

C. the smallest particle of a substance that is representative of the substance.

What never changes when two or more objects collide is

C. the total momentum of all the objects

When 90 kJ is removed from a 2-kg copper bar, its temperature drops from 200°C to 85°C. The specific heat of copper is

D. 0.39 kJ/kg°C.

Of these substances, the one with the lowest specific heat is

D. gold

Steam at 100°C is more dangerous than the same mass of water at 100°C because the steam

D. releases a great deal of heat when it condenses.

A refrigerator

D. removes heat from a region and carries it elsewhere.

The average pressure of the atmosphere at sea level corresponds to which one or more of the following?

E. 101 kPa and 15 lb/in2 are both correct.

A gold ball and a ping-pong ball are dropped in a vacuum chamber. When they have fallen halfway down, they have the same

A. speed

Sublimation refers to

A. the vaporization of a solid without first becoming a liquid.

Molecular motion in a gas is the minimum possible at

C. 0 K.

chapter 5

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A 100-kg astronaut ejects 4 g of gas from her propulsion pistol at a speed of 50 m/s. Her recoil speed is

A. 0.2 mm/s

The work you do in raising an orange from your waist to your mouth is roughly

A. 1 .

A total of 4900 J is expended in lifting a 50-kg mass, The mass is raised to a height of

A. 10 m

A 1-kg object is moving at 10 m/s. To double its kinetic energy, its speed should be increased to approximately

A. 14 m/s

The mass equivalent of 6.0 MJ is

A. 6.7 C 10^-11 kg

An 800-kg car moving at 80 km/h collides head-on with a 1200-kg car moving at 40 km/h in the opposite direction. If they stick together, the wreckage now has an initial speed of

A. 8 km/h

Which of the following formulas relating temperatures on the Celsius and Fahrenheit scales is correct?

A. Tc= (5/9) (Tf- 32)

When a gas is forced into a smaller volume without a change in temperature, its pressure increases because its molecules

A. strike the container walls more often.

Of the substances below, the one with the highest specific heat is

A. water

The melting point of water is 0°C. Its freezing point is

B. 0°C.

A 90-kg llama has an average power output of 80 W. The minimum time the llama can go up a hill 500 m high is

C. 1.5 h

The 2.5-kg head of an ax exerts a force of 80 kN as it penetrates 18 mm into the truck of a tree. The speed of the ax head when it strikes the tree is

C. 34 m/s

An 800-kg car moving at 80 km/h overtakes a 1200-kg car moving at 40 km/h in the same direction. I the two cars stick together, the wreckage has an initial speed of

C. 56 km/h

The specific heat of ice is 2.1 kJ/kg°C. When 50 kJ of heat is removed from 2 kg of ice initially at -5°C, the final temperature of the ice is

D. -17°C.

A moving object does not necessarily have

D. potential energy

Which of the following formulas expresses the relationship between the pressure and absolute temperature of a gas sample whose volume is fixed?

p1/t1=p2/t2

A horse has a power output of 11 hp (746 W) when it is pulling a cart. If the cart covers 100 m in 30 s, the force the horse exerts on the cart is

A. 0.22kN

A heat engine absorbs heat at 127°C and exhausts heat at 77°C. Its maximum efficiency is

A. 13 percent.

A sedentary person requires about 6 million J of energy per day. This rate of energy consumption is equivalent to about

A. 70 W.

A weightlifter raises a 200-kg barbell through a height of 2 m in 2.2 s. The average power he develops during the lift is

C. 1.78 kW

A 1-kg mass has a KE of 1 J when its speed is

C. 1/4 m/s

A 400-kg concrete block is 1 m long, 0.6 m wide, and 0.3 m high. It can exert three different pressures on a horizontal surface, depending on which face it rests on. The highest pressure is

C. 13.1 kPa.

The specific heat of water is 4.2 kJ/kg°C. The heat needed to warm 8 kg of water from 20°C to 70°C is

C. 1680 kJ.

A container holds 1 g of air at atmospheric pressure. When an additional gram of air is pumped into the container and there is no change in temperature, the new pressure is

C. 2 atm.

A typical metabolic rate while walking is

C. 300 W.

The density of brass is 8 × 103 kg/m3. The volume occupied by 320 g of brass is

C. 38 cm3.

A 400-kg concrete block is 1 m long, 0.6 m wide, and 0.3 m high. Its density is

C. 667 kg/m.

A temperature of 20°C is the same as

C. 68°F.

To prevent it from tumbling in flight, a projectile such as a football is sent off spinning. The physical principle involved is

C. conservation of angular momentum

The density of air is 1.3 kg/m3. The air in a room 5 m long, 4 m wide, and 2.5 m high has a mass of

D. 65 kg.

The specific heat of water is 4.2 kJ/kg°C. How long will it take for a 2-kW heating element to raise the temperature of 30 kg of water from 20°C to 80°C?

D. 84 min

The watt is a unit of

D. Power

Which of the following quantities is always the same to all observes?

D. The speed of light

Which of the following is not true of molecular motion in a gas?

D. There is a definite average direction of motion at a given temperature.

The pressure at the bottom of a barrel filled with liquid does not depend on the

D. area of the liquid surface.

Radiation is emitted

D. by liquids, solids, and gases.

Which of the following quantities is independent of the size and shape of n object composed of given material?

D. density

The maximum possible efficiency of a heat engine

D. depends on the ratio between the exhaust and intake temperatures.

The entropy of a system is a measure of its

D. disorder.

When the speed v of an object of mass m approaches he speed of light c, its kinetic energy

D. is more than 1/2 mv^2 and can exceed 1/2 mc^2

When a liquid freezes to become a solid,

D. it gives off heat.

When the speed of an object is doubled

D. its momentum is doubled

In the formula E0+mc^2, the symbol c represents the speed of

D. light

A thermometer calibrated in the Celsius scale and a thermometer calibrated in the Fahrenheit scale are used to measure the same temperature. The numerical reading on the Fahrenheit thermometer

D. may be smaller or larger than that on the Celsius thermometer.

Which of the following is (are) not a unit of power?

A. Joule-second

A Celsius thermometer and an absolute thermometer are used to measure the temperature of the same gas sample. The readings on the thermometers are respectively TC and TK. Which is correct?

A. TC is smaller than TK.

The height above the ground of a child on a swing varies from 0.5 m at the lowest point to 2.0 m at the highest point. The maximum speed of the child is

A. about 5.4 m/s

The sun

A. attracts light waves passing nearby

Heat transfer in a vacuum

A. can take place only by radiation.

In an isolated system, entropy

A. cannot decrease.

Suppose there were molecules that had no attraction whatsoever for one another. A collection of such molecules would form a

A. gas

Molecules are, in general, farthest apart from one another in

A. gases.

The heat a refrigerator absorbs from its contents is

A. less than it gives off.

The physics of a heat engine cannot be used to understand the operation of a

A. nuclear reactor.

The KE of a 900-kg car whose speed is 60 km/h is

B. 125 kJ.

A 1-N weiht has a PE relative to the ground of 1 J when it is a height of

B. 1m

The linear momentum of a 400-kg giraffe galloping at 5 m/s is

B. 2000 kgm/s

The speed of a 1000-kg car whose KE IS 450 kJ is

B. 30 m/s

In order to double the average energy of the molecules in a gas at 200 K, its temperature must be changed to

B. 400 K.

If it is to be 40 percent efficient, a heat engine that exhausts heat at 350 K must absorb heat at a minimum temperature of

B. 583 K.

Ethanol boils at 172°F. The Celsius equivalent of this temperature is

B. 78°C.

When heat is added to a body of matter, the resulting temperature increase does not depend upon

B. Its shape

A barometer measures

B. atmospheric pressure

The freezing point of a substance is always lower than its

B. boiling point.

In order to operate, a heat engine must have

B. both a hot and a cold reservoir.

The work output of every heat engine

B. equals the difference between its heat intake and heat exhaust.

A bowling ball rolling in a level ground at the speed v strikes a basketball at rest. The basketball moves off in the original direction of the bowling ball

B. faster than v while the bowling ball continues slower than v

Rolling a ball up an inclined plank requires an amount of work proportional to the

B. height the ball is raised

The first law of thermodynamics is the same as the

B. law of conservation of energy.

If a spaceship 100 m long when at rest on the Earth were to travel at nine-tenths the speed of light, its length as measured by on observer on the Earth would be

B. less than 100 m.

A cake of soap is placed in a bathtub sink. The buoyant force on the soap is

B. less than its weight.

A rocket is fired in space. As it moves, the total momentum of the rocket and its exhaust gasses

B. remains the same

A sample of a gas is expanded to twice its original volume while its temperature is held constant. Relative to their original average energy, the new average energy of the molecules is

B. the same.

According to the general theory of relativity, gravitation

C. is a distortion in space-time

The temperature of a gas sample in a rigid container is reduced. The pressure the gas exerts on the container walls decreases because

C. its molecules have lower average speeds and so strike the walls less often with less momentum.

The pressure on the bottom of an object inside a liquid is

C. more than the pressure on its top.

Heat transfer by convection occurs

C. only in liquids and gases.

When a skater pulls in her arms to turn faster, her angular momentum

C. remains the same

One liter of hydrogen gas at atmospheric pressure is allowed to expand to a volume of 3 liters with the temperature held constant. If the average speed of the hydrogen molecules was originally v, their new average speed is

C. v.

Heat transfer by conduction occurs

D. in liquids, solids, and gases.

A horizontal force is applied to a 2-kg ball on a smooth table. The balls speed is 8 m/s when it has gone 4 m. The magnitude of the force is

D. 16 N

A 40-kg boy climbs a vertical ladder at 0.5 m/s. His power output is

D. 196 W.

A ball whose momentum is mv strikes a wall and bounces off. The change in the balls momentum is

D. 2 mv

Fifty kJ of heat is added to a 10-kg piece of lead at its melting point of 330°C and 2 kg of lead melts. The heat of fusion of lead is

D. 25 kJ/kg.

When a ton of coal burns, it loses 3.3 10^-7 kg of mass. The energy given off is

D. 3.0 10^10 J

A 1-N weight has a KE of 1 J when its speed is

D. 4.4 m/s

Which one or more of the following is a vector quality?

E. linear momentum and angular momentum