Question

A rock on the ground weighs 40N. How much force does the ground exert on the rock?

Answer 1

Answer:

The correct option is;

C. 40 N

Explanation:

Given that the rock is on the ground, we have;

The weight of the rock, $F_W$ = 40 N ↓

From Newton's third law of motion, we have that action and reaction are equal and opposite,

Therefore, given that the weight of the rock exerts a force of 40 N on the ground, and the rock is stable and stationery on the ground, then the ground is reacting to the weight of the rock with an equal force of 40 N, acting in opposite direction to the weight of the block to balance the weight of the rock and create equilibrium such that the net force acting on the rock is zero

∑F = $F_W + F_R$ = 0

Where;

$F_R$ = The reaction of the ground

We have;

$F_W$ + $F_R$= 40 + $F_R$  = 0

$F_R$ = 0 - 40 = -40

$F_R$ = -40 N ↓

∴ $F_R$ = 40 N ↑.