Contributions of Different Scientists to the Study of Energy

Conservation of Energy, Momentum, and Mechanical Energy

In physics, the law of conservation of energy states that the total energy of an isolated system

remains constant—it is said to be conserved over time. Energy can neither be created nor destroyed;

rather, it transforms from one form to another.

One of the most powerful laws in physics is the law of momentum conservation. ... For a collision

occurring between object 1 and object 2 in an isolated system, the

total momentum of the two objects before the collision is equal to the total momentum of the two

objects after the collision.

Mechanical energy is the sum of kinetic and potential energy in an object that is used to do work. In other words, it is energy in an

object due to its motion or position, or both.

Equation 5.1:EA = EB

Equation 5.2:

KEA + PEA = KEB + PEB

Conserving

The pictures above illustrate the concept of momentum. Recall that

momentum ( p ) is a vector quantity which is equal to the product of the

mass (m) of an object and the change in its velocity( v ). In symbols:

p = m v

Recall Newton’s second law of motion where the net force Fnet is equal to the product of mass m

and acceleration a.Fnet = ma

You know that acceleration (a) is the rate of change of velocity over time ( v/ t) , so:

Fnet = m v/ t

Rearranging the equation, you have:F t = m v

F t = p

Two types of collisions:

Elastic

Inelastic

Elastic collisions are collisions in which both momentum and kinetic energy

are conserved. The total system kinetic energy before the collision equals the total system kinetic energy after the collision. If total kinetic energy is not

conserved, then the collision is referred to as an inelastic collision.

Inelastic Collision

A collision between bodies in which part of their kinetic energy is transformed to another form of energy, tending to result in the slowing or joining together of the bodies.