Complete question is;
Shoveling snow can be extremely taxing since the arms have such a low efficiency in this activity. Suppose a person shoveling a sidewalk metabolizes food at the rate of 800 W. (The efficiency of a person shoveling is 3%.)
(a) What is her useful power output? (b) How long will it take her to lift 3000 kg of snow 1.20 m? (This could be the amount of heavy snow on 20 m of footpath.) (c) How much waste heat transfer in kilojoules will she generate in the process?
Answer:
A) P_out = 24 W
B) t = 1470 s
C) Q = 1140.72 KJ
Explanation:
We are given;
Input Power; P_in = 800 W
Efficiency; η = 3% = 0.03
A) Formula for efficiency is;
η = P_out/P_in
Making P_out the subject, we have;
P_out = η•P_in
P_out = 0.03 × 800
P_out = 24 W
B) We know that;
Power = work done/time taken
Thus;
P_out = mgh/t
We are given;
m = 3000 kg
h = 1.20 m
Thus, time is;
t = (3000 × 9.8 × 1.2)/24
t = 1470 s
C) amount of heat wasted is calculated from;
Q = (P_in - P_out)t
Q = (800 - 24) × 1470
Q = 1,140,720 J
Q = 1140.72 KJ
Answer:
2274 J/kg ∙ K
Explanation:
The complete statement of the question is :
A lab assistant drops a 400.0-g piece of metal at 100.0°C into a 100.0-g aluminum cup containing 500.0 g of water at 15 °C. In a few minutes, she measures the final temperature of the system to be 40.0°C. What is the specific heat of the 400.0-g piece of metal, assuming that no significant heat is exchanged with the surroundings? The specific heat of this aluminum is 900.0 J/kg ∙ K and that of water is 4186 J/kg ∙ K.
= mass of metal = 400 g
= specific heat of metal = ?
= initial temperature of metal = 100 °C
= mass of aluminum cup = 100 g
= specific heat of aluminum cup = 900.0 J/kg ∙ K
= initial temperature of aluminum cup = 15 °C
= mass of water = 500 g
= specific heat of water = 4186 J/kg ∙ K
= initial temperature of water = 15 °C
= Final equilibrium temperature = 40 °C
Using conservation of energy
heat lost by metal = heat gained by aluminum cup + heat gained by water
Answer:
9.78 m/s²
Explanation:
To solve this, we use the gravitational formula
g = GM/r², where
g = acceleration due to gravity
G = gravitational constant
M = mass of the planet
r = radius of the planet
From the question, we got that the mass of the planet is
M = 9ME, where ME = 5.95*10^24
M = 9 * 5.95*10^24
M = 5.355*10^25 kg
Also, the Radius of the planet, R = 3RE, where RE = 6.37*10^6
R = 3 * 6.37*10^6
R = 1.911*10^7 m
On applying the values of both R and M to the equation, we get
g = GM/r²
g = (6.67*10^-11 * 5.355*10^25) / (1.911*10^7)²
g = 3.57*10^15/3.65*10^14
g = 9.78 m/s²
Therefore, the acceleration due to gravity on the planet is 9.78 m/s²
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SONAR stands for "sound navigation and ranging,” and it is used to map and explore the ocean floor.
Answer:
below
Explanation: When a liquid changes into a gas vaporization has occurred. The process can either occur due to boiling or evaporation. Boiling occurs when the vapor pressure of the liquid is raised (by heating) to the point where it is equal to the atmospheric pressure.
