If a 490 mL ordinary glass beaker is filled to the brim with ethyl alcohol at a
ID: 249120 • Letter: I
Question
If a 490 mL ordinary glass beaker is filled to the brim with ethyl alcohol at a temperature of 5.20°C,
how much will overflow when their temperature reaches 22.0°C? mL
(b) How much less water would overflow under the same conditions? mL
2- Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a total of 14 rubs a distance of 7.50 cm each and with a frictional force averaging 30.0 N, what is the temperature increase? The mass of tissue warmed is only 0.100 kg, mostly in the palms and fingers.
°C
A 2.00 g lead bullet traveling at 460 m/s strikes a target, converting its kinetic energy into thermal energy. It's initial temperature is 40.0°C. Find the available kinetic energy of the bullet.
J
Find the heat required to melt the bullet.
J
Suppose you stand with one foot on ceramic flooring and one on a wool carpet, making contact over an 78.0 cm2 area with each foot. Both the ceramic and the carpet are 1.50 cm thick and are 10.0°C on their bottoms. At what rate must each foot supply heat to keep the top of the ceramic and carpet at 33.0°C?
wool carpet
W
ceramic tile
W
(1 How many kilograms of water must evaporate from a 55.0 kg woman to lower her body temperature by 0.770°C?
1 kg
(2Is this a reasonable amount of water to evaporate in the form of perspiration, assuming the relative humidity of surrounding air is low?
Yes No
Radiant heat makes it impossible to stand close to a hot lava flow. Calculate the rate of heat loss by radiation from 1.00 m2 of 1230°C fresh lava into 25.0°C surroundings, assuming lava's emissivity is 1.
kW
What is the change in internal energy of a system that takes in 2.80 106 J of heat, and does 4.50 105 J of work while dissipating 8.00 106 J of heat?
J
Explanation / Answer
1) Assuming that the volume of the beaker remains constant, because the volume extension for a
rigid material is much smaller than for a liquid.
use
V = v0(1 + *T) where is the volume temperature extension coefficient
for ethyl alcohol = 1.4*10^-3 K^-1
for water = 0.206*10^-3 K^-1
the new volume for the alcohol:
V = 490(1 + 1.4*10^-3*16.8) = 501.52
overflow = 11.52mL
new volume of the water:
V = 490(1 + 0.206*10^-3*16.8) = 491.70
overflow = 1.70 mL
less overflow of water = 11.52 - 1.70 = 9.82
2) The work done by the friction force is equal to the amount of thermal energy which is transferred.
Work = Ff * Total distance in meters
7.50 cm = 0.075 m, Distance back and forth = 0.150 m
Total distance = 14 * 0.150 = 2.1 m
Work = 30 * 2.1 = 63 N * m
This is the amount of thermal energy which was transferred to the tissue.
Q = mass * Specific heat * T
You need to know the specific heat of the tissue.
the average specific heat of the human body is 3470 J/(kg * C)
63 = 0.1 * 3470 * T
T = 63 ÷ 347 0.1815