Answer
a. $2.5\times10^{-4}m^2$
b. $7.5m^2$
c. $149m^2$
d. On the item, on the roof, and neither (respectively)
Work Step by Step
The area of the solar cell is the power required, divided by $20\%$ of the received intensity.
a. $A=\frac{P}{I_{effective}}=\frac{50\times10^{-3}W}{200W/m^2}=2.5\times10^{-4}m^2$
b. $A=\frac{P}{I_{effective}}=\frac{1500W}{200W/m^2}=7.5m^2$
c. $A=\frac{P}{I_{effective}}=\frac{40hp(746W/hp)}{200W/m^2}=149m^2$
d. The calculator’s solar panel is small enough to be mounted directly on it.
The hair dryer’s solar panel is small enough to be mounted on a house roof.
The car’s solar panel is NOT small enough to be mounted directly on it.