The braking force needed to bring a 4000-kg truck to a stop from a speed of 20 m/s in 5 s is
A) 1000 N.
B) 1633 N.
C) 9800 N.
D) 16,000 N.

Question

Quizplus · Accepted Answer

The braking force can be calculated using Newton's second law, $F = ma$, where $m$ is the mass and $a$ is the acceleration. First, find the acceleration needed to stop the truck in 5 seconds from 20 m/s, which is $a = \Delta v / t = (0 - 20) / 5 = -4 \, m/s^2$. The negative sign indicates deceleration. Then, the force is $F = ma = 4000 \times -4 = -16,000 \, N$. The negative sign indicates the direction of the force is opposite to the motion, but in magnitude, it's 16,000 N.

The Braking Force Needed to Bring a 4000-Kg Truck to a Stop