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) $\mathrm{\Delta}\mathbf{p}_{1} = - \mathrm{\Delta}\mathbf{p}_{2}$
B) $\mathrm{\Delta}E = - \mathrm{\Delta}(PE + KE) = 0$
C) $\mathbf{F\ \mathrm{\Delta}}t = m\mathrm{\Delta}\mathbf{v}$
D) $\mathrm{\Delta}\mathbf{x \propto \mathrm{\Delta}F}$
Where symbols have their usual meaning
Explanation
(c) Change of momentum F $\mathbf{\mathrm{\Delta}}t = m\mathrm{\Delta}\mathbf{v}$
$\mathbf{\Longrightarrow \ \ }\mathbf{F} = \frac{m\mathrm{\Delta}\mathbf{v}}{t}$
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.