Question

A boy climbs up a hill, which rises 1 m in every 25 secs, on his bicycle. The mass of the boy and his bicycle is 120 kg. What is the power applied by the boy if he is cycling at the rate of 6km/hour?

• A. 80 watt
• B. 54.7 watt
• C. 100 watt
• D. 120 watt

Answer 1

The correct option is B 54.7 watt

The mass of the boy and the bicycle is $m=120kg$ , Velocity is , $v=6km/h$

Here the boy and his bicycle rises $1m$ in every $25$ seconds

$Sothetotalworkdonebytheboyandhisbicycleis,W=\frac{1}{2}m{v}^2+mgh=(\frac{1}{2}\times 120\times 36\times \frac{5}{18}\times \frac{5}{18})+(120\times 10\times 1)=\frac{500}{3}+1200=1366\cdot 67JNowthepowerappliedbytheboyis,P=\frac{W}{t}=\frac{1366\cdot 67}{25}=54\cdot 67J/s=54.7W$