Question

A 63-gram chicken egg falls to the ground in your rocket, hitting the ground at 20.0 m/s. If the egg is brought to rest in 0.20 seconds, how big is the net force on the egg? Show all work, including equations and substitutions with units.

Answer 1

According to Newton's Second Law of Motion, the net force is equal to the product of mass and acceleration; F=ma where m=mass and a is equal to acceleration.

Before you start on this, you need to first sort out your given:
m = 63 grams
a = ?
F= ?
You will notice that you have two unknowns, you can use the other given to solve for one of them, which is acceleration.

You can compute acceleration for this problem with this formula:

a =
`(vf - vi)/(t)`

where: vf = final velocity which is the last velocity recorded
vi = initial velocity which is the first velocity recorded
t = time which is the length of time passed as the velocity changed.

In your case, the egg was falling initially at 20 m/s then was brought to rest in 0.20 seconds.

Because the motion of the egg is going downwards, your velocity is negative. So your given is then:

vi = -20 m/s
vf = 0 m/s (because it was brought to rest, meaning it is not moving anymore)
t = 0.20 seconds

Now all you have to do is input that into your formula:

a =
`(0 m/s - (-20m/s))/(0.20s)` =
`(20m/s)/(0.20s)`

Your answer should be
`100m/s^(2)`

Now that you have your acceleration, you can go back to the first equation:

If you want to get your answer in Newtons or (N) you must first convert the mass into kilograms. So your given will then be 0.063 kg. So your new equation will be:

Fnet =
`(0.063kg)(100m/s^(2) ) = 6.3 kg.m/s^(2) or 6.3 N`

* NOTE:
`kg.m/s^(2)` is the SI unit of N (newtons)