Energy and Momentum
by
Video Lecture 5 of 46
Not yet rated
Views: 1,543
Date Added: February 5, 2015

### Lecture Description

It is of great importance that the ideas of ENERGY and MOMENTUM be clearly
distinguished and understood. Mathematically, momentum is M x V or MV.
Energy - more exactly kinetic energy - is 1/2 MV^. We need not worry here
where the 1/2 comes from. Momentum is the consequence of a force acting for
a time: F x t. Energy is the consequence of a force acting over a distance: ___
Thus it is with the two cars:
The force acting on both cars is the same. The force acts for the same time on both. The force acts for a greater distance on the little car and for a lesser distance on the bigger car.
Accordingly: The F x t is the same for both.
Therefore their momenta are equal. The F x S for the little car is greater than the F x s for the bigger car. Therefore their energies are UNequal.
We show an array of DEMONSTRATIONS bearing on ENERGY and MOMENTUM.

1 - On a curved track the ball can go no higher to a remote end than the height
from which it was released.

2 - We drive a nail into a block of wood. The energy delivered to the system
by the moving hammer is spent in splitting the wood and raising the temperature of the nail and the wood. Friction always produces heat.

3 - We demonstrate acoustic energy which arises from the mechanical energy
of my moving vocal cords.

4 - Thermal energy communicated to a kernel ,of corn makes it "pop" . The
expansion of the water in the corn is enormous.

5 - We rub a rod of bakelite (hard-rubber) with a piece of fur. This mechanical
work separates the electric charges and "creates" electrostatic energy.

6 - A pile-driver delivers the potential energy of the driver to the nail.

7 - A spring is compressed; potential energy is stored. This energy can push
a ball upward when the spring "recovers" .

8 - In shooting a gun we hold it tightly against the shoulder so the "kick"
less.

9 - A child's toy stores "elastic" energy in a wound-up rubber band. This
stored energy can drive the car backwards.

10 - A geared-wheel is turned by mechanical force. The energy thus stored can heat a metal to incandescence - that is - hot enough to emit light, Thus mechanical energy produces heat and light.

We show a likeness of Christiaan Huygens, a Dutchman, who contributed to our understanding of these things.

### Course Description

Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics. The series was also released in the United States under the title Science Demonstrations.

This program was a series of 45 shows (approximately 15 minutes each) on various topics in physics, organized into 3 units: Mechanics; Heat and Temperature / Toys; and Waves and Sound / Electricity and Magnetism.

## Comments

There are no comments. Be the first to post one.
 Post comment as a guest user. Click to login or register: Your name: Your email:(will not appear) Your comment:(max. 1000 characters) Are you human? (Sorry)