Potential Energy and energy conservation

In summary: No, internal energy and work done by non-conservative forces are not the same. Internal energy refers to the total energy within a system, while work done by non-conservative forces refers to the energy transferred to or from a system by forces that do not conserve energy.
  • #1
kyin01
47
0
Hi everyone, so I was going to start on my HW but there was some things confusing me when reading the book.
This is calculus based (feel free to use integrals) and we are on the concept of potential and total mechanical energy and such.1) This new chapter we are on introduces
Work[tex]_{grav}[/tex]=mgh[tex]_{1} - [/tex]mgh[tex]_{2}[/tex] (1 being above 2) and

Work[tex]_{el}[/tex]=.5kx[tex]_{1}[/tex] [tex]^{2}[/tex] - .5kx[tex]_{2}[/tex] [tex]^{2}[/tex]

However in the previous chapter we were told that W[tex]_{net}[/tex]=[tex]\Delta[/tex]K[tex]_{energy}[/tex] or W=F[tex]\bullet[/tex] [tex]_{net}[/tex] [tex]\vec{s}[/tex]

So my question is, if the Work introduced now the same kind of work as we were told in the previous chapter?
I tried setting an quick example, let's assume we throw a ball of 10kg vertically upwards and it reaches a maximum height of 5m and than goes back down. Gravity is 10[tex]\frac{m}{s^{2}}[/tex]. So let's pretend no air resistance and such and we are trying to find work.
If I use this equation W=F[tex]_{net}[/tex][tex]\bullet[/tex][tex]\vec{s}[/tex], I get work is = to 50J
but if I use the new equation Work[tex]_{grav}[/tex]=mgh[tex]_{1} - [/tex]mgh[tex]_{2}[/tex], work is = to 500

So what is it I am not understanding? Are they 2 different kind of work?2) Is internal energy (U[tex]_{int}[/tex]) the same as work done by non conservative forces (W[tex]_{nc}[/tex])?

edit: i have no idea why the subscripts appear as superscripts, I tried editing and fix but it still appears as superscripts. If it's not clear enough please let me know I'll make them into pictures in MSPaint and post or something
 
Physics news on Phys.org
  • #2
kyin01 said:
So my question is, if the Work introduced now the same kind of work as we were told in the previous chapter?
Sure.
I tried setting an quick example, let's assume we throw a ball of 10kg vertically upwards and it reaches a maximum height of 5m and than goes back down. Gravity is 10[tex]\frac{m}{s^{2}}[/tex]. So let's pretend no air resistance and such and we are trying to find work.
If the ball goes up and down, the net work done by gravity is zero. (The work is negative on the way up, positive on the way down.)

Let's say you want the work done by gravity when a ball falls from a height of 5m to the ground, which is what I think you were calculating.
If I use this equation W=F[tex]_{net}[/tex][tex]\bullet[/tex][tex]\vec{s}[/tex], I get work is = to 50J
How did you get this? The force = mg = 100N. If we call the distance h=5m, the work done = mgh = (100)*5 = 500 J.
but if I use the new equation Work[tex]_{grav}[/tex]=mgh[tex]_{1} - [/tex]mgh[tex]_{2}[/tex], work is = to 500
This also gives you mgh = 500 J.
 
  • #3
Ahh, sorry I see it now. Thanks

So is Is internal energy the same as work done by non conservative forces?
 

1. What is potential energy?

Potential energy is the energy an object possesses due to its position or condition. It is stored energy that has the potential to do work in the future.

2. What are the different types of potential energy?

The types of potential energy include gravitational potential energy, elastic potential energy, chemical potential energy, and nuclear potential energy.

3. How is potential energy related to energy conservation?

The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. Therefore, potential energy is just one form of energy that can be converted into other forms, such as kinetic energy, while still obeying the law of conservation of energy.

4. How can potential energy be calculated?

The formula for calculating potential energy is PE = mgh, where PE is potential energy, m is the mass of the object, g is the acceleration due to gravity, and h is the height or distance from the reference point. This formula applies to gravitational potential energy, while other types of potential energy may have different formulas.

5. How is energy conservation important in our daily lives?

Energy conservation is important in our daily lives because it helps us to use energy more efficiently, reducing our overall energy consumption and lowering our impact on the environment. It also helps to save money on energy bills and promotes sustainability for future generations.

Similar threads

  • Introductory Physics Homework Help
Replies
15
Views
300
  • Introductory Physics Homework Help
Replies
11
Views
1K
Replies
8
Views
218
  • Introductory Physics Homework Help
Replies
5
Views
524
  • Introductory Physics Homework Help
Replies
3
Views
604
  • Introductory Physics Homework Help
Replies
8
Views
1K
Replies
7
Views
236
  • Introductory Physics Homework Help
Replies
12
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
658
  • Introductory Physics Homework Help
2
Replies
55
Views
1K
Back
Top