Ncert Exercises & Solutions

A man squatting on the ground gets straight up and stands. The force of reaction of the ground on the man during the process is

1.	constant and equal to mg in magnitude.
2.	constant and greater than mg in magnitude.
3.	variable but always greater than mg.
4.	at first, greater than mg and later becomes equal to mg.

(d) Hint: Apply Newton's laws of motion.

Step 1: Find the reaction force on the man.

When the man is squatting on the ground he is tilted somewhat, hence he also has to balance frictional force besides his weight in this case,

R = reaction force = friction + mg

$\Rightarrow$ R > mg

When the man gets straight up in that case friction z 0

$\Rightarrow$ Reactional = mg