Shoveling snow can be extremely taxing because the arms have such a low efficien
ID: 1458247 • Letter: S
Question
Shoveling snow can be extremely taxing because the arms have such a low efficiency in this activity - around 3.00%. Suppose a person shoveling a footpath metabolizes food at the rate of 810 W. A) What is her useful power output, in watts? B) How long, in minutes, will it take her to lift 3100 kg of snow 0.5 m? C) The energy that doesn't go into shoveling snow is lost in heat - how much heat is wasted, in kilojoules, during this process? Shoveling snow can be extremely taxing because the arms have such a low efficiency in this activity - around 3.00%. Suppose a person shoveling a footpath metabolizes food at the rate of 810 W. A) What is her useful power output, in watts? B) How long, in minutes, will it take her to lift 3100 kg of snow 0.5 m? C) The energy that doesn't go into shoveling snow is lost in heat - how much heat is wasted, in kilojoules, during this process? A) What is her useful power output, in watts? B) How long, in minutes, will it take her to lift 3100 kg of snow 0.5 m? C) The energy that doesn't go into shoveling snow is lost in heat - how much heat is wasted, in kilojoules, during this process?Explanation / Answer
Here ,
efficiency = 0.03
power output = 810 W
useful power = efficiency * power input
useful power = 810 * 0.03
useful power = 24.3 W
the useful power output is 24.3 W
b)
let the time taken is t
m*g*h = power * time
3100 * 9.8 * 0.5 = 24.3 * t
t = 625.1 s = 10.41 min
the time taken to lift the snow is 10.41 min
c)
energy lost in heat = 810 * 625.1 - 3100 * 9.8 * 0.5
energy lost in heat = 491143 J
the energy lost in heat is 491 kJ