Question

An athlete in the Olympic games covers a distance of $100$m in $10$s. His kinetic energy can be estimated to be in the range

• A. $2\times {10}^{5}J-3\times {10}^{5}J$
• B. $20,000J-50,000J$
• C. $2,000J-5,000J$
• D. $200J-500J$

Answer 1

Answer: (C)

$2,000J-5,000J$

Given,

Total distance covered $=100m$

Total time taken $=10s$

Then,

The average speed, $v=\frac{Distance}{Time}=\frac{100}{10}=10m/s$

Now,

Kinetic Energy $=\frac{1}{2}m{v}^2$

It is clear that the $K.E$ depends on both mass and speed. Mass is not given in the question. Suppose it lie between $40kg$ to $100kg$

Then,

$\frac{1}{2}\times 40\times {10}^2<K.E.<\frac{1}{2}\times 100\times {10}^2$

$2000J<K.E<5000J$

Thus the range of kinetic energy will be $2000J$ to $5000J$