A 13-kg mass initially at rest has a net force applied to it. The force causes the mass to reach a velocity of 12 m/s in eight seconds. The magnitude of the force is
A) 15 N.
B) 20 N.
C) 30 N.
D) 25 N.

Question

Quizplus · Accepted Answer

The magnitude of the force can be found using Newton's second law, $F = ma$, where $F$ is the force, $m$ is the mass, and $a$ is the acceleration. First, find the acceleration using the formula $a = \frac{\Delta v}{\Delta t}$, where $\Delta v$ is the change in velocity and $\Delta t$ is the change in time. Here, $\Delta v = 12 \, \text{m/s}$ (final velocity) - 0 \, \text{m/s}\) (initial velocity) = $12 \, \text{m/s}$, and $\Delta t = 8 \, \text{s}$. So, $a = \frac{12 \, \text{m/s}}{8 \, \text{s}} = 1.5 \, \text{m/s}^2$. Then, using $F = ma$, $F = 13 \, \text{kg} \times 1.5 \, \text{m/s}^2 = 19.5 \, \text{N}$, which rounds to $20 \, \text{N}$, making option B correct.

A 13-Kg Mass Initially at Rest Has a Net Force