# Force exerted to a falling object

• Perdition
In summary, using the law of conservation of energy, the velocity of the rock just before collision was found to be 6.3 m/s. The velocity becomes 0 due to resistance force, which leads to an acceleration of 330.75 m/s^2. Multiplying this by the mass of the rock (120 N/9.8 m/s^2), the Earth's average force of resistance is calculated to be approximately 4.1 kN.

## Homework Statement

A rock with a weight of 120 N free falls from height of 2.00m collides with with Earth and digs 60 mm into it. What is the Earth's average force of resistance

## Homework Equations

F=m*g => m=F/g

m*g*h = 1/2*m*v^2

v=√(2*g*h)

## The Attempt at a Solution

I found the velocity of a rock just before collision using the law of conservation of energy. I now know the velocity which I got 6.3 m/s but now I am stumped on how do i find the forces exerted by Earth to stop the rock from digging deeper.

Last edited:
Hmm i would do it another way

Before hitting ground its velocity is 6.3m/s right??

So that velocity becomes 0 due to some acceleration (due to resistance force)

so using v2-v02=2(a)(s)

u find acceleration (retardation in this case)

now that multiplied to the mass will give u the force...

Hope it helps

Think of the 20mm as a 'stopping distance'.

i assume you substitute s with 0.006 m right. I tried that in that case

$v^{2}_{f}$=$v^{2}_{i}$ + 2 * a * x

0=6.3^{2}+2*a*0.06
0=39.69+0.12a
-0.012a=39.69 / (-0.12a)
a=330.75 m/s^2

F=m*a

F= 12 * 330.75 = 3969 N

however the answer should be 4.1 kN

Last edited:
use mass = 120/9.8

getting closer :P thanks I guess it was just an error in rounding the number

## What is the force exerted on a falling object?

The force exerted on a falling object is called the weight. It is equal to the mass of the object multiplied by the acceleration due to gravity.

## How does the force exerted on a falling object change during its fall?

The force exerted on a falling object remains constant throughout its fall. This is because the acceleration due to gravity, which determines the weight, remains constant near the Earth's surface.

## What factors affect the force exerted on a falling object?

The force exerted on a falling object is affected by its mass and the strength of the gravitational field it is falling in. Air resistance may also play a role in the force exerted on the object.

## Does the shape of a falling object affect the force exerted on it?

The shape of a falling object may affect the force exerted on it due to air resistance. Objects with a larger surface area will experience more air resistance and therefore may experience a different force than objects with a smaller surface area.

## What is the relationship between force exerted and the speed of a falling object?

The force exerted on a falling object is directly proportional to its acceleration, which is also directly proportional to its speed. This means that as the speed of a falling object increases, so does the force exerted on it.