Question

a stone with a mass of 100 kg sits on the ground. gravity acts on the stone at a rate of 9.8 m/s². what is the normal force acting on the stone, keeping it at rest? (1 point)
98 n
9.8 n
980 n
91.2 n

Explanation:

Step1: Identify relevant formula

Use Newton's second - law $F = ma$. In the vertical direction, since the stone is at rest, the net force $F_{net}=0$. The forces acting on the stone in the vertical direction are the gravitational force $F_g$ and the normal force $F_N$. So $F_{net}=F_N - F_g=0$, which implies $F_N = F_g$.

Step2: Calculate gravitational force

The formula for gravitational force is $F_g=mg$, where $m = 100\ kg$ and $g = 9.8\ m/s^2$. So $F_g=100\times9.8=980\ N$.

Step3: Determine normal force

Since $F_N = F_g$, then $F_N = 980\ N$.

Answer:

980 N