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Question
A 50-kg sack is lifted 2 m in the same time as a 25-kg sack is lifted 4 m. The power expended in raising the 50-kg sack compared to the power used to lift the 25-kg sack isA) twice as much.
B) half as much.
C) the same.
Answer
This answer is hidden. It contains 1 characters.
Related questions
Q:
Which requires more energy?
A) melting a gram of 0C ice
B) increasing the temperature of 1 gram of water from 0C to 100C
C) changing 1 gram of 100C water to 100C steam
D) all the same
Q:
In walking barefoot on red-hot coals, providing that bits of coal do not stick to your feet, it would be safer if your feet are
A) wet.
B) dry.
C) either of these
D) none of the above
Q:
As a block of ice at 0C melts, the block absorbs energy
A) and decreases in temperature.
B) and increases in temperature.
C) without a temperature change.
D) all of the above
E) none of the above
Q:
When snow falls, the surrounding air is normally
A) cooled.
B) warmed.
C) both of these
D) none of the above
Q:
When a gas changes phase to become a solid, energy is
A) absorbed.
B) released.
C) unchanged.
Q:
Foreign ions introduced to water
A) lower the freezing point of water.
B) raise the freezing point of water.
C) do not affect water's freezing point.
Q:
When bringing water to a boil in the mountains, the time needed to reach the boiling point is
A) less than at sea level.
B) more than at sea level.
C) the same as at sea level.
Q:
A good cook knows that the temperature of violently boiling water is
A) higher than that of simmering water.
B) the same as that of simmering water.
C) actually lower than 100C.
D) neither of the above
Q:
When water boils, energy added to the water is counteracted by
A) decreased pressure in the water.
B) static equilibrium.
C) energy carried away by steam.
D) energy of the whole system.
E) none of the above
Q:
A mixture of light and heavy molecules make up a sample of gas. If the temperature of the gas is constant, then all the molecules have the same average
A) speed.
B) kinetic energy.
C) both of these
D) none of the above
Q:
Sublimation is a change of phase from solid to gas without
A) passing through the liquid phase.
B) a transfer of energy.
C) a change of temperature.
Q:
The molecules in a room-temperature glass of water jostle around at
A) various speeds.
B) much the same speed.
C) constant speeds.
Q:
Long ago a runaway greenhouse effect greatly transformed the planet
A) Mercury.
B) Venus.
C) Mars.
D) none of the above
Q:
The planet Earth loses heat primarily by
A) conduction.
B) convection.
C) radiation.
D) all of the above
E) none of the above
Q:
When you leave your warm house for an hour or so on a cold day, to save energy you should turn the thermostat
A) down.
B) up.
C) off.
D) to room temperature.
Q:
A good reflector of radiation is a
A) good absorber of radiation.
B) good emitter of radiation.
C) poor absorber of radiation.
D) none of the above
Q:
A piece of pizza is normally a net radiator of energy when its temperature is
A) higher than its surroundings.
B) lower than its surroundings.
C) neither of these
Q:
If an object radiates more energy than it absorbs, its
A) thermal energy decreases.
B) temperature decreases.
C) both of these
D) none of the above
Q:
Radiant energy emitted by our planet is
A) terrestrial energy.
B) the outcome of radioactivity in Earth's interior.
C) electromagnetic.
D) all of the above
Q:
If a volume of air is warmed, it expands. If a volume of air expands, it
A) warms.
B) cools.
C) neither of these
Q:
Blow on your hand and you feel the warmth of your breath. Pucker your lips so your breath expands as you blow and your breath is
A) still warm.
B) cool.
C) neither of these
Q:
Coastal winds that shift from night to day illustrate
A) conduction.
B) convection.
C) radiation.
D) all about equally
Q:
A water-filled paper cup held in a flame will not catch fire because
A) the inside of the paper is wet.
B) water is an excellent conductor of heat.
C) paper is a good conductor of heat.
D) the paper cup cannot become appreciably hotter than the water it contains.
Q:
A bare roof of a warmly heated home on a snowy day indicates
A) an unwanted flow of heat.
B) good insulation.
C) a change of phase.
D) all of the above
Q:
If you were caught in freezing weather with only a candle for warmth, you would be warmer in
A) an igloo.
B) a tent.
C) a wooden house.
Q:
Which of these are good insulators?
A) feathers
B) wood
C) snow
D) all the above
E) none of the above
Q:
In practice, a good insulator
A) stops heat flow.
B) slows heat flow.
C) speeds negative heat flow.
D) all of the above
Q:
Thermal energy is measured in
A) calories.
B) Calories.
C) joules.
D) any or all of the above for special cases
Q:
Heat is thermal energy that matter
A) contains.
B) transfers.
C) both of these
D) none of the above
Q:
Heat energy is measured in units of
A) degrees.
B) joules.
C) calories.
D) both joules and calories.