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

Answer 1

Answer: (D)

The average speed of the athelete
$v=\frac{100}{10}=10\, m / s$
$\therefore \text { K.E. }=\frac{1}{2} mv ^2$
If mass is $40\, kg$ then, K.E. $=\frac{1}{2} \times 40 \times(10)^2=2000 \, J$
If mass is $100 \, kg$ then,
$\text { K.E. }=\frac{1}{2} \times 100 \times(10)^2=5000\, J$