Test: Work, Energy And Power
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- 1.If two substances of equal mass are supplied the same amount of thermal energy and their final temperatures are different, you can assume that they have
- A.
Different heat capacities
- B.
The same volume
- C.
Different abilities to conduct heat
- D.
Different densities
- E.
Different volumes
- 2.How much heat is required to raise the temperature of 40 g of water 20°C? (cw = 4.18 ´ 103 J/kg·°C)
- A.
5.2 J
- B.
3.3 x 103 J
- C.
8.0 x 10–1 J
- D.
3.3 x 105 J
- E.
2.1 x 106 J
- 3.The transfer of heat through a material by collision of the atoms is called
- A.
Heat transfer
- B.
Convection
- C.
Radiation
- D.
Heat exchange
- E.
Conduction
- 4.A 2000-W tennis ball machine releases 0.028-kg balls at a speed of 100 m/s in 0.20 s. The efficiency of the machine is
- A.
70%
- B.
14%
- C.
28%
- D.
1.4%
- E.
7.0%
- 5.If a block of iron and a slice of watermelon are left in a refrigerator for a looooong period of time, compare the temperatures of both when they are immediately removed from the refrigerator.
- A.
The iron will have a colder temperature than the watermelon.
- B.
The watermelon will have a colder temperature than the iron.
- C.
The iron will feel colder because it is a good conductor of heat which is drawn from your fingers.
- D.
The iron will feel colder because it has a very high specific heat capacity.
- E.
They both feel equally cold.
- 6.At midnight, you walk outside. The temperature of the air has been exactly -12 Celcius for several hours. You touch a metal fence post, a block of wood, and some snow. Apply the concept of thermal equilibrium to identify the correct statement.
- A.
The fence post has the lowest temperature.
- B.
The block will have the highest temperature.
- C.
The fence post, the block of wood, and the snow will all be at a temperature of -12 Celcius.
- D.
The process of thermal equilibrium causes cold to flow from objects with low specific heat capacities.
- E.
Determining which object will have the lowest temperature is impossible without knowing the specific heat capacities.
- 7.When water at 100 Celcius is cooled to 50 Celcius, which of the following is true?
- A.
The kinetic energy of the water molecules remains constant, while heat energy is being released to its surroundings.
- B.
The kinetic energy of the water molecules is increasing, while heat energy is being absorbed by the molecules.
- C.
Heat energy from the surroundings is being used to increase the kinetic energy of the water molecules.
- D.
The kinetic energy of the water molecules is being transferred to heat energy being released to its surroundings.
- E.
Only the kinetic energy of the particles is being increased.
- 8.A 50 W immersion heater is switched on for 1 minute to heat up a cup of water. How much energy is supplied to the water?
- A.
50 J
- B.
1000 J
- C.
2000 J
- D.
3000 J
- E.
0.833 J
- 9.In the ice ages, cave men and women didn’t have pots and pans they could set on the fire to heat water for tea. Instead, they had tightly woven waterproof bags and dropped hot rocks from the fire into the water-filled bag to heat the water. If the specific heat of water is 1 cal/goC and the specific heat of rock is 0.1 cal/goC, how many grams of rocks at 200oC must be added to 100 grams of water to raise the water temperature from 20oC to 80oC?
- A.
200 g
- B.
500 g
- C.
667 g
- D.
1250 g
- E.
1470 g
- 10.A 100-gram ice cube at 0oC is dropped into 100 grams of water at 20oC. When the ice melts, what will be temperature of the water? The latent heat of fusion for water is 333000 J/kg and the specific heat capacity of water is 4186 J/kgoC. (Hint: First, determine the amount of ice the water would be able to melt.)
- A.
1.2 Celcius
- B.
1.8 Celcius
- C.
2.0 Celcius
- D.
11.3 Celcius
- E.
0 Celcius (not all the ice melts)
- 11.The fact that desert sand is very hot in the day and very cold at night is evidence that sand has a
- A.
Low specific heat capacity
- B.
High specific heat capacity
- C.
Low heat of fusion
- D.
High heat of fusion
- E.
Problem
- 12.It is necessary to determine the specific heat of an unknown object. The mass of the object is 227.0 g. It is determined experimentally that it takes 16.0 J to raise the temperature 10.0oC. Find the specific heat capacity of the object.
- A.
0.001,40 J/kg K
- B.
7.05 J/kg K
- C.
3,630,000 J/kg K
- D.
1600 J/kg K
- E.
None of the above
- 13.A blacksmith heats a 1.1kg iron horseshoe to 550 degree Celsius, then plunges it into a bucket containing 15 kg of water at 20 degree Celsius. What is the final temperature? Assume that the transfer of heat is 100% efficient. (specific heat water = 1 cal/goC; iron = 0.107 cal/goC).
- A.
42 Celcius
- B.
15 Celcius
- C.
48 Celcius
- D.
96 Celcius
- E.
99 Celcius
- 14.How long will it take a 500W microwave oven to vaporize completely a 500g block of ice that is initially at zero degree Celsius? (Lf = 334 kJ/kg; cw = 4.184 kJ/kg°C, Lv = 2257 kJ/kg) (Hint: This could be a long one, just be patient and work out the solution)
- A.
1 min
- B.
10 min
- C.
1 hour
- D.
10 hours
- E.
1 day
- 15.A 621.0-g iron meteor impacts the earth at a speed of 1922.0 m/s. If its energy is entirely converted to heat of the meteorite, what will the resultant temperature rise be? (The specific heat for iron is 447 J/kg°C.)
- A.
6.30 Celcius
- B.
63 Celcius
- C.
16300 Celcius
- D.
2430 Celcius
- E.
4000 Celcius
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