A 4.00-g lead bullet is traveling at a speed of 200 m/s when it embeds in a wood post. If we assume that half of the resultant heat energy generated remains with the bullet, what is the increase in temperature of the embedded bullet? (specific heat of lead = 0.0305 kcal/kg/C, 1 kcal = 4 186 J)
a. 78.3 C
b. 157 C
c. 313 C
d. 39.2 C
e. 97.9 C
[Ques. 2] A resistor is made of a material that has a resistivity that is proportional to the current going through it. If the voltage across the resistor is doubled, what happens to the current through it?
a. It doubles.
b. It quadruples.
c. It increases by a factor of 23/2.
d. It increases by a factor of 21/2.
[Ques. 3] An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended into heat for warming water. What minimum power must be generated if 210 g water (enough for 1 cup of coffee) is to be heated in 14.0 min from 26.0C to 84.0C? (1 cal = 4.186 J, the specific heat of water is 4 186 J/kg/C)
a. 3 640 W
b. 289 W
c. 60.7 W
d. 850 W
e. 42.5 W
[Ques. 4] A copper cable needs to carry a current of 160 A with a power loss of only 2.0 W/m. What is the required radius of the copper cable? (The resistivity of copper is 1.7 108 m).
a. 0.43 cm
b. 0.83 cm
c. 1.7 cm
d. 2.6 cm
e. 0.33 cm
[Ques. 5] An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended into heat for warming water. How much mechanical energy is required to increase the temperature of 200 g of water (enough for 1 cup of coffee) from 18C to 94C? (1 cal = 4.186 J, the specific heat of water is 4 186 J/kg/C)
a. 6.4E+4 J
b. 3.2E+4 J
c. 1.6E+4 J
d. 1.0E+3 J
e. 1.5E+1 J
[Ques. 6] Number 10 copper wire (radius = 1.5 mm) is commonly used for electrical installations in homes. What is the voltage drop in 20 m of 10 copper wire if it carries a current of 12 A? (The resistivity of copper is 1.7 108 m.)
a. 0.58 V
b. 0.48 V
c. 2.7 V
d. 2.4 V
e. 0.34 V
[Ques. 7] Marc attaches a falling 328-kg object with a rope through a pulley to a paddle wheel shaft. He places the system in a well-insulated tank holding 23.2 kg of water. When the object falls, it causes the paddle wheel to rotate and churn the water. If the object falls a vertical distance of 88.6 m at constant speed, what is the temperature change of the water? (1 kcal = 4 186 J, the specific heat of water is 4 186 J/kg/C, and g = 9.80 m/s2)
a. 17 000 C
b. 2 930 C
c. 2.93 C
d. 0.587 C
e. 5.87 C
[Ques. 8] A Nichrome wire has a radius of 1.3 mm and a resistivity of 1.5 106 m. If the wire carries a current of 1.8 A, what is the potential difference per unit length along this wire?
a. 0.19 V/m
b. 0.51 V/m
c. 0.66 V/m
d. 6.4 V/m
e. 5 V/m
[Ques. 9] On a sunny day at the beach, the reason the sand gets so hot and the water stays relatively cool is attributed to the difference in which property between water and sand?
a. mass density
b. specific heat
c. temperature
d. thermal conductivity
[Ques. 10] A Nichrome wire has a radius of 1.3 mm and a resistivity of 1.5 106 m. What is the resistance per unit length of this wire?
a. 0.37 /m
b. 8.0 /m
c. 3.6 /m
d. 0.28 /m
e. 1.2 /m
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