potential energy and energy conservation

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POTENTIAL ENERGY AND ENERGY CONSERVATION Reported by: Ida Lyn A. Azuelo BSED Physics 3 Physics for Secondary Teachers

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POTENTIAL ENERGY AND

ENERGY CONSERVATIONReported by:

Ida Lyn A. AzueloBSED Physics 3

Physics for Secondary Teachers 1

Potential Energy

• The energy associated with the position of a system rather than its motion

Gravitational Potential Energy

• Potential energy associated with a body’s weight and its height above the ground

m – mass of the bodys – displacementy - vertical componentsw – weight (mg)Fother - some forces acting on the body

m – mass of the bodys – displacementy - vertical componentsw – weight (mg)Fother - some forces acting on the body

The quantity (y1 –y2) is

negative, and Wgrav is

negative because the weight and

displacement are in opposite

direction.

Gravitational Potential Energy

Conservation of Mechanical Energy(Gravitational Forces Only)

Work- Energy TheoremWtot = ΔK = K2 - K1

Wtot = Wgrav = -ΔUgrav = Ugrav,1 - Ugrav,2

ΔK = -ΔUgrav K2 - K1 = Ugrav,1 - Ugrav,2

K1 + Ugrav,1 = K2 + Ugrav,2

If only gravity does work

Total Mechanical Energy of the System

E = K + Ugrav

Potentialenergy

kineticenergy

E1 = K1 + Ugrav,1 E2 = K2 + Ugrav,2CONSTANT

When only the force of gravity does work, the total mechanical energy is constant—that is, it is

conserved.

CONSERVATION OF MECHANICAL

ENERGY

Problem Sample

You throw a 0.145-kg baseball straight up, giving it an initial velocity of magnitude 20.0

m/s. Find how high it goes, ignoring air resistance.

When Forces Other Than Gravity Do Work

Wother + Wgrav = K2 - K1

Wgrav = Ugrav,1 - Ugrav,2

Wother + Ugrav,1 - Ugrav,2 = K2 - K1

K1 + Ugrav,1 = K2 + Ugrav,2

If forces other than gravity do work

Elastic potential energy

• The process of storing energy in a deformable body such as a spring or rubber band in terms of elastic potential energy.

• A body is called elastic if it returns to its original shape and size after being deformed.

F = kx

F – force on the springk - force constant of the springx - displacement

Work done on a spring

Work done by a spring

Elastic Potential Energy

The work done by all forces other than the gravitational force or elastic force equals the change in the total mechanical energy E = K + U of the system, where U = Ugrav

+ Uel is the sum of the gravitational potential energy and the elastic potential energy.

Conservative Force and

nonConservative Force

A force that offers this opportunity of two-way conversion between kinetic

and potential energies CFNFA force that is not conservative

The Law of Conservation of Energy

Energy is never created or destroyed; it only changes form.

THANK YOU FOR LISTENING!!!!

POTENTIAL ENERGY AND

ENERGY CONSERVATIONReported by:

Ida Lyn A. AzueloBSED Physics 3

Physics for Secondary Teachers 1