The resistance ( R ) to a motion of a car is partly constant and partly varies as the square of the speed ( V ) When the car is moving at ( 20KM/H ) The resistance is (720 OHMS ) and at ( 60KM/H ) the resistance is 232 ohms fine an expression for ( R ) of ( V ) the resistance at 40km/h

3 answers

R = c + kV^2
when V = 20, R = 720
c + 400k = 720

when V = 60, R = 232
c + 3600k = 232

subtract the two equations ...
3200k = -488
k = -61/400

back in first equation:
c + 400(-61/400) = 720
c = 781

R = 781 - (61/400) V^2

Now that we have the equation, you can finish your question.

SIR

SAMUEL