###### 1. Braking Distance Formula

The following table is taken from a
Virginia Division of Motor Vehicles Manual

and it shows the Reaction
Distance, the Braking Distance, and the Total Stopping

Distance at
various speeds.

The Reaction Distance is the distance that your car travels from the
time that the

driver sees the need to do so until his foot hits the brake.

The braking distance is the distance that the car travels after the
brakes are applied

until it comes to a stop.

The Total Stopping Distance is the sum of the Reaction Distance and
the Braking Distance.

from the Learner's Manual of the Virginia DMV

Here are the formulas to compute those distances:

Note that both the braking distance and the total stopping distance
formulas are

quadratic, and therefore their graphs are parabolas.

2. Heater

Heaters are sold which make use of the
relection property of the parabola.

The heat source is at the focus
and heat is concentrated in parallel rays.

Have you walked by the
parabolic reflector heater at COSTCO?

3. Satellite Dishes

Satellite Dishes work on this same principle.

Incoming waves are concentrated to the focus.

4. Automonbile Headlights

An automobile headlight is another example of a Paraboloid of Revolution --

taking a parabola and rotating it about its axis of symmetry.

The smooth inner surface of the headlight is a glass reflector upon which

bright aluminum has been deposited. This part is a powerful reflector.

A parabolic reflector has the property that if a light source is placed at the

focus of the reflector, the light rays will reflect from the mirror as rays

parallel to the axis.

This is used in auto headlights to give an intense concentrated beam of light.

For safer night driving, we do not want all the light rays to be parallel

to the axis. Some light must be aimed far down the road, to the side, upward

for signs or bridges.

So we offset the filament from the focus and change the beam entirely.

In most of today's cars, a 4 Lamp System is used -- 2 filament sealed beam

units in 2 lamps.

The position of the filaments accomplishes most of the desired illumnination

patterns. The rest is taken care of by special lenses which contain prisms

to bend the light rays.

5. McDonald's Arches

McDonald's Arches are parabolas.

Actually, Carl Letsche sent in a correction about the Golden Arches not being parabolas.

Click here for the link

6. Fountains

Bellagio's fountains at Las Vegas exhibit water in the shapes of parabolas.

7. Path of a Ball

Gallileo was the first to show that the path of an object thrown in space
is a parabola.

8. Golden Gate Bridge

The cables that act as suspension are parabolas.

9. Le Four Solaire at Font-Romeur

There is a reflector in the Pyrenees Mountains that is 8 stories high.

It cost two million dollars to build and it took ten years to build it.

It is made of 9,000 mirrors arranged in a parabolic mirror.

It can reach 6,000 degrees Fahrenheit just from the Sun!

10. Parabolic mirror

A parabolic mirror at the Seattle Science Museum.

11. Parabolic Receivers

A person who whispers at the focus of one of the parabolic reflectors

can be heard
by a person located near the focus of the other parabola.