# Homework Help: Efficiency, power, irradiance and speed problem

1. Oct 24, 2012

### TyErd

1. The problem statement, all variables and given/known data
I've attached the question

2. Relevant equations
The problem is I dont know what equation(s) I have to use.

3. The attempt at a solution
This question my part of my thermofluid dynamics course but I cannot find a formula in my textbook that uses an irradiance (1000W/m^2) term.

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2. Oct 24, 2012

### RTW69

Think about this problem. You have a 1 m2 solar collector. It is 30% efficient. If 1000 W/m2 is falling on a 1 m2 that is 30% efficient how much power is the solar panel producing(in KW)? Compare with the power of the car.

3. Oct 24, 2012

### TyErd

so that means 300W or 0.3kW of power is being produced.
0.3/200=0.0015
how do i relate this to speed

4. Oct 24, 2012

### CWatters

If it takes 200,000W to go at speed X how much faster is it likely to go if the power available is increased to 200,300W ? Hint: it's a multiple choice question and its not going to go >50% faster :-).

5. Oct 25, 2012

### TyErd

yes its fair enough that it wont go 50% faster or 10% or even 4%, but how would I go about getting an exact answer?

6. Oct 26, 2012

### aralbrec

How about W=Fd, P = F*v, assume F doesn't change (much)

Last edited: Oct 26, 2012