Question

A person of weight 60 kg wants to loose 5 kg by going up and down 10m high stairs. Assume he burns twice as much fat while going up than going down. If 1 kg of fat is burnt on expending 7000 kcal. How many times must he go up and down to reduce his 7 kg weight? (Take $g=10{ms}^{-2})$

• A. $1.8\times {10}^3$ times
• B. $2.4\times {10}^3$ times
• C. $1.7\times {10}^3$ times
• D. $2.1\times {10}^3$ times

Answer 1

The correct option is C $1.7\times {10}^3$ times

Energy used to go up $=mgh=60\times 10\times 10=6000J$

Energy used to come down $\frac{6000}{2}=3000J$

Energy used in one round trip $=9000J$

$1cal=4.5J$

$1J=\frac{1}{4.2cal}$

$9000J=\frac{9000}{4.2}=2142.85cal$

$7000kilocal$ is required to burn $1kg$ mass

To reduce $5kg$ mass, energy required $=7000\times 5=35000kiloval$

Number of trip $=\frac{35000\times 1000}{2142.85}=1.7\times {10}^3$