Question

The force required to row a boat over the sea is proportional to the speed of the boat. If it is found that it takes $24$ h.p. to row a certain boat at a speed of $8km/hr$, then the horsepower required when speed is doubled is :

• A. $12h.p$
• B. $48h.p.$
  
• C. $96h.p.$
  
• D. $192h.p.$
  

Answer 1

The correct option is C $96h.p.$

$F\propto V$.

Power is given as $P=FV\propto V^2$

$\frac{P_1}{P_2}=(\frac{V_1}{V_2}{)}^2$

$\frac{24}{P_2}=(\frac{V_1}{2V_1}{)}^2$

$P_2=4\times 24=96hp$