<span>In real machines, efficiency is always less than 1 .</span>
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:
Gamma rays occupy the short-wavelength end of the spectrum; they can have wavelengths smaller than the nucleus of an atom. Visible light wavesare one-thousandths the width of human hair--about a million times longer than gamma rays. Radio waves, at the long-wavelength end of the spectrum, can be many meters long.
Answer:
The answer to your question is : vf = 15.18 m/s
Explanation:
Data
vo = 24 m/s
d = 120 m
vf = ? when d = 60.0 m
Formula
vf² = vo² + 2ad
For d =100m
a = (vf² - vo²) / 2d
a = (0 -24²) / 2(100)
a = -576/200
a = 2.88 m/s²
Now, when d = 60
vf² = (24)² - 2(2.88)(60)
vf² = 576 - 345.6
vf² = 230.4
vf = 15.18 m/s
If iodine is added to a starch solution, they react with each other and the iodine darkens to an almost pitch black.
however, if iodine is added to a solution containing no starch, it will show up only as an extremely pale brown. almost colorless and hardly visible.
when following the changes in some inorganic oxidation reduction reactions, iodine may be used as an indicator to follow the changes of iodide ion and iodine element. soluble starch solution is added. only iodine element in the presence of iodide ion will give the characteristic blue black color. neither iodine element alone nor iodide ions alone will give the color result.
hope this answer really helps your question :)
