The force rquired to row a boat at constant velocity is proportional to the velocity . If it takes 10 horse power to row a ceteqain boat at a speed of 5km/h how much horse power does it take to row it at a speed of 15km/h?

Options

A. 90
B. 60
C. 30
D. 45

Answer

A

Explanation

Power P = (force F) `xx` (velocity v) `therefore P = Kv^(2)` (given , F = kv)
`therefore (P_(2))/(P_(1)) = ((v_(2))/(v_(1)))^(2) = ((15)/(5))^(2) = (9)/(1)` or ` P_(2) = 9 xx P_(1) = 9 xx 10 = 90` HP