# Can someone help explain the normal force as the average force in a pile driver?

• LuckyIam
In summary, the conversation is about a practice problem in which a steel hammerhead is being used to drive an I beam into the ground. The question is asking for the speed of the hammerhead when it hits the I beam, as well as the average force exerted on the I beam by the hammerhead. The solution involves using the work energy theorem and solving for the average force, which is represented by the variable "n." The conversation also includes a discussion about the different variables and their meanings in the equation.
LuckyIam
Hey everyone, this is a copy/paste from a another thread. I actually don't need help with finding an answer. Its a practice problem in the book so its all worked out. What I need is for someone to help explain to me why the normal force is the average...I'm having trouble understanding this part1. Homework Statement

In a pile driver , a steel hammerhead with mass 200kg is lifted 3m above the top of a vertical I beam being driven into the ground. the hammer is then dropes driving the Ibeam7.4cm farther into the ground. The vertical rails that guide the hammerhead exert a constant 60N friction force on the hammerhead. Use the work energy theorem to find a) speed of the hammerhead just as it hits the I beam andb) the average force the hammerhead exerts on the I-Beam Ignore the air effects of the air.

## The Attempt at a Solution

I managed to understand part a. Part b is where I am lost.

The book shows the following work, and I need help understanding on of the steps.

Wtotal = (w-f-n)s23

Wtotal = (w-f-n)s23 = k3-k2

*** n is the same as g right? and we solve for n? Since when is n the average force?***

n = w-f - k3-k2/s23

=1960N - 60N - 0J - 5700J / 0.074m

=7900N

the part underlined I understand.
The part in bold is where I can't explain why.

LuckyIam said:
Wtotal = (w-f-n)s23

Wtotal = (w-f-n)s23 = k3-k2
I need to know what all these variables represent.
LuckyIam said:

the part underlined I understand
Good.

Well, let me guess: 2 is when the hammer hits, 3 is when the 7.4 cm are done. s23 is then the 0.74 m.

So what you have is some kind of energy equation:
Ekin, 2+Epotential, 2 = Workbeam + Workfric +Epotential, 3

with Workbeam the energy used to drive the I beam down
and Workfric the energy lost in friction.

Workbeam is s23 * average force, hence the average force.

Probably forgot the brackets in

1960N - 60N - ( 0J - 5700J ) / 0.074m

AND a zero in the result.

Have pity with the poor helpers who desperately try to understand what you type: read what you typed as if you were one of them.

## 1. What is a hammer and nail used for?

A hammer and nail are commonly used together in construction and woodworking projects. The nail is inserted into the surface to be joined and the hammer is used to strike the nail, securing it in place.

## 2. How do I properly use a hammer and nail?

To use a hammer and nail, first hold the nail in place on the surface you want to join. Then, use the hammer to gently tap the nail into the surface, making sure it is straight and secure. Continue hammering until the nail is fully inserted into the surface. Be careful not to hit your fingers!

## 3. What are the different types of hammers and nails?

There are many different types of hammers and nails, each designed for different purposes. Some common types of hammers include claw hammers, ball peen hammers, and sledgehammers. Nails come in various sizes and shapes, including common nails, finishing nails, and roofing nails.

## 4. How do I remove a nail from a surface?

To remove a nail, use the claw end of a hammer to grip the nail and gently pry it out of the surface. You can also use a nail puller or pliers to remove a nail. Be careful not to damage the surface or the nail in the process.

## 5. Can I reuse nails?

It is not recommended to reuse nails. Nails can become bent or damaged during use, making them less effective for future projects. It is best to use new nails for each project to ensure a strong and secure hold.

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