Q. Consider the following statement: When jumping from some height, you should bend your knees as you come to rest, instead of keeping your legs stiff. Which of the following relations can be useful in explaining the statement
A) $\mathrm{\Delta}\overrightarrow{P_{1}} = - \mathrm{\Delta}\overrightarrow{P_{2}}$
B) $\mathrm{\Delta}E = - \mathrm{\Delta}(PE + KE) = 0$
C) $\overrightarrow{F}\mathrm{\Delta}t = m\mathrm{\Delta}\overrightarrow{v}$
D) $\mathrm{\Delta}\overrightarrow{x} \propto \mathrm{\Delta}\overrightarrow{F}$
Explanation
(c) $\overrightarrow{F}\mathrm{\Delta}t = m\mathrm{\Delta}\overrightarrow{v} \Rightarrow F = \frac{m\mathrm{\Delta}\overrightarrow{v}}{\mathrm{\Delta}t}$
By doing so time of change in momentum increases and impulsive force on knees decreases
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.