Question

Heat engines take input energy in the form of heat, use some of that energy to do work, and exhaust the remainder. Similarly, a person can be viewed as a heat engine that takes an input of internal energy, uses some of it to do work, and gives off the rest as heat. Suppose a trained athlete can function as a heat engine with an efficiency of 0.10. (a) What is the magnitude of the internal energy that the athlete uses in order to do 1.5x104 J of work? (b) Determine the magnitude of the heat the athlete gives off.

Answer 1

a).
`Q_(h)=1.5x10^5J`

b).
`Q_(c)=13.2x10^3J`

Step-by-step explanation:

a).

Using the law of thermodynamic and using to isovolumetric

ΔU=Qh

`Q_(h)=(W_(net))/(Efficiency)`

So to determine the internal energy knowing the work it do

`Q_(h)=(1.5x10^4J)/(0.10)=1.5x10^5J`

b).

Efficiency is the work done in relation of the work apply in this case to produce heat so:

`E=(Q_(h)-Q_(c))/(Q_(h))`

Solve to Qc

`Q_(c)=Q_(h)*[1-E]`

`Q_(c)=1.5x10^4J*(1-0.10)`

`Q_(c)=13.2x10^3J`