applied physics presentation
TRANSCRIPT
Applied Physics
Mr. Bobbitt
Sir Isaac Newton• Sir Isaac Newton is credited
for discovering Gravity: One day Newton was sitting in an orchard under an apple tree and noticed apples falling to the ground. Maybe an apple hit him on the head and maybe it didn’t. Like all good scientists, Newton collected and examined the data (the apple) and ate it.
Law of Gravity• All particles of matter are
attracted to all other particles of matter with an attraction that is directly proportional to the masses of the objects and inversely proportional to the distance between the objects.
OR
• There is an attraction between all things.
• After developing the Law of Gravity, Newton continued to work with objects of matter and determined how they reacted with each other. This work led him to the development of what is now called:
PHYSICS
Newton’s Three Laws of Motion
Newton’s First Law of MotionThe Law of Inertia
• Objects at rest stay at rest unless acted upon by an unbalanced force and objects in motion stay in motion in a straight line and at a constant speed unless acted upon by an unbalanced force.
Newton’s Second Law of MotionThe Law of Acceleration
• Objects acted upon by an unbalanced force accelerate in the direction of the force directly proportional to the magnitude of the force and inversely proportional to the mass of the object.
Newton’s Third Law of Motion The Law of Action and Reaction
• For every action by a force there is an equal and opposite reaction by a different force.
G-Force
• The “G” stands for Gravity.• Currently you are at 1 G• If you weighed 100 pounds and went to 2 G
you would FEEL like you weighed 200 pounds.
Positive G Forces
• Upward acceleration.• Forces blood away from the brain and toward
the feet.• A typical person can withstand around 5 g
before G-LOC.
Negative G Forces
• Negative g’s are usually experienced during a steep dive in an aircraft where you would feel your weight lessening.
• As little as 2-3 g’s would cause your eyes' blood vessels to start rupturing. This is called a "red out".
ExamplesGs
Bugatti Veyron from 0 to 100 km/h in 2.4 s 1.18
High-g roller coasters 3.5–6.3
Top fuel drag racing world record of 4.4 s over 1/4 mile
4.2
Sprint Missile 100
Rating of electronics built into military artillery shells
15,500
Effects on Body• A normal healthy person would start
experience loss of vision at around 5-6 g• Roller coasters give forces of maximum up
to 3 to 4 g's for brief periods of time. • If a force of 4 to 6 g's is held for more than a
few seconds, the results could be devastating; such as blackouts to death.
• The devastating car crash of Princess Diana of Wales in 1997 was estimated to range somewhere between 70–100 g's. This accident was intense enough to pull the pulmonary artery from her heart.
Links
• Roller Coaster Design• How Roller Coasters Work• Roller Coaster Design PBS Kids
Catapultsand
Simple Machines
Mr. Bobbitt
Simple Machines
• A mechanical device that provides a change in force that creates a mechanical advantage.
• Changing the direction of a force.• Few or no moving parts.
Energy
• The ability to do work.
Work
• Results of force moving an object.
Gravity
• Gravity is the force that constantly pulls objects toward Earth.
What is a Lever?What is a Lever?
• A hammer is a lever that helps do work.• Work is done whenever force makes an object
move.
What is an Inclined Plane?
• A ramp is an inclined plane.• A ramp helps move objects.• You can use an inclined plane to help move an
object to a higher or lower place.
What is a Wedge?
• A doorstop is a wedge.• A wedge is a simple machine used to push
objects apart.• An ax is a wedge that splits wood.
What is a Screw?
• A screw is a simple machine used to hold objects together.
• Think about your desk.• Does it have screws helping to hold it
together?
What is a Wheel and Axle?
• A wheel and axle is a simple machine made of a rod attached to the center of a wheel.
• The axle, or rod, turns when you put force on the wheel.
• You probably have seen a wheel and axle on cars, skateboards, etc.
What is a Pulley?
• A pulley is a simple machine with a wheel and with a rope.
• The rope fits around the edge of the wheel.• You can use a pulley to move a load up, down
or sideways.
Links
• How Can I Help?• Simple Machines
What is a Catapult?
• In modern times, the word catapult can be used to describe any machine that hurls a projectile.
• 3 Types– Onager– Ballista– Trebuchet
Onager
• One Arm or Lever• Torsion Device– Twisted rope or rubber
bands to create tension.
• Gift from the Romans
Ballista
• This machine was deliberately invented by the Greeks, around 800 BCE.
• Ballista were even mounted on warships and used to hurl fire onto other ships.
• Functions similar to a crossbow or sling shot.
Trebuchet• The Trebuchet is probably
the oldest type of catapult. • It was invented either by the
Chinese or in the middle east.
• Trebuchets were used mainly as lobbing machines to spread fire and diseased corpses, as well as a lot of solid missiles, over the walls of castles to rain down on the inhabitants.
Ideas
Necessary Forces
SpeedInstant Stop (Energy Transfer)
Best ways to increase distance:1. Apply more force2. Longer Lever3. Less Weight in Projectile4. Angle of Release
Links
• Catapult Game• Master of Catapult• Design and Test a Catapult• How Can I Help?
CO2 Cars
Mr. Bobbitt
Speed equals distance divided by time.
s=d/t
Speed
Force• Force is the push or pull exerted on an object.• The magnitude of a force can be found by multiplying
the mass and the acceleration of the object.• Force equals mass times acceleration.
Aeroforces
Shape• “Slippery” – the
object slips through the air.
• Air should glide over smoothly as well as go under.
• Even a mirror or door handle that sticks out can detour performance.
Drag
• The faster an object travels the more the drag.
• Drag can reduce speed because it will trace the overall top of the car.
• Any mistakes or areas that aren’t smooth will create a drag force.
• Drag actually pushes in the opposite direction you want to go.
Lift
• Lift goes underneath the car and pushed upward.
• Lift can reduce speed by actually lifting the car off the ground.
Friction• Force that opposes
motion. • This force comes from
the axle rubbing the hole that was drilled for it.
• To eliminate this take your pencil and “color” the axle.
• Friction is often the force that brings objects to rest.