What is the average stopping force on a 55 kg person who comes to a sudden stop in 0.2 seconds from a speed of 18 m/sec?

To find the average stopping force on the person, we can use Newton's second law of motion, which states that force is equal to mass times acceleration (F = ma). In this scenario, we need to determine the acceleration, or in this case, the deceleration, since the person is coming to a stop.

First, it’s necessary to find the change in velocity. The person is initially moving at a speed of 18 m/s and comes to a stop, meaning their final velocity is 0 m/s. The change in velocity (Δv) is therefore:

Δv = final velocity - initial velocity = 0 m/s - 18 m/s = -18 m/s.

Next, we need to calculate the acceleration. Acceleration is defined as the change in velocity over the time taken for that change:

a = Δv / Δt.

Given that the time taken (Δt) is 0.2 seconds:

a = -18 m/s / 0.2 s = -90 m/s².

The negative sign indicates that this is deceleration. Now, we can find the average stopping force by substituting the mass and acceleration into the formula F = ma:

F = (55 kg)(-90