Question

When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is ________.a. less than 1/10 as great. b. more than 1/10 as great. c. about 1/10 as great.d. about 10 times as great.

Answer 1

Answer:

c. about 1/10 as great.

Explanation:

While jumping form a certain height when we bend our knees upon reaching  the ground such that the time taken to come to complete rest is increased by 10 times then the impact force gets reduced to one-tenth of the initial value when we would not do so.

This is in accordance with the Newton's second law of motion which states that the rate of change in velocity is directly proportional to the force applied on the body.

Mathematically:

$F\propto\frac{d}{dt} (p)$

$\Rightarrow F=\frac{d}{dt} (m.v)$

since mass is constant

$F=m\frac{d}{dt}v$

when $dt=10t$

then,

$F'=m.\frac{v}{10\times t}$

$F'=\frac{1}{10} \times \frac{m.v}{t}$

$F'=\frac{F}{10}$ the body will experience the tenth part of the maximum force.

where:

$\frac{d}{dt} =$ represents the rate of change in dependent quantity with respect to time

$p=$ momentum

$m=$ mass of the person jumping

$v=$ velocity of the body while hitting the ground.