Sir Isaac Newton• Sir Isaac Newton is creditedfor discovering Gravity:One day Newton was sittingin an orchard under anapple tree and noticedapples falling to the ground.Maybe an apple hit him onthe head and maybe itdidn’t. Like all goodscientists, Newton collectedand examined the data (theapple) and ate it.
Law of Gravity• All particles of matter areattracted to all other particles ofmatter with an attraction that isdirectly proportional to themasses of the objects andinversely proportional to thedistance between the objects.OR• There is an attraction betweenall things.
• After developing the Law of Gravity, Newton continued towork with objects of matter and determined how theyreacted with each other. This work led him to thedevelopment of what is now called:PHYSICSNewton’s Three Laws ofMotion
Newton’s First Law of MotionThe Law of Inertia• Objects at rest stay at rest unless acted upon by anunbalanced force and objects in motion stay inmotion in a straight line and at a constant speedunless acted upon by an unbalanced force.
Newton’s Second Law of MotionThe Law of Acceleration• Objects acted upon by an unbalanced forceaccelerate in the direction of the force directlyproportional to the magnitude of the force andinversely proportional to the mass of the object.
Newton’s Third Law of MotionThe Law of Action and Reaction• For every action by aforce there is an equaland opposite reaction bya different force.
G-Force• The “G” stands for Gravity.• Currently you are at 1 G• If you weighed 100 pounds and went to 2 Gyou would FEEL like you weighed 200 pounds.
Positive G Forces• Upward acceleration.• Forces blood away from the brain and towardthe feet.• A typical person can withstand around 5 gbefore G-LOC.
Negative G Forces• Negative g’s are usually experienced during asteep dive in an aircraft where you would feelyour weight lessening.• As little as 2-3 g’s would cause your eyesblood vessels to start rupturing. This is called a"red out".
ExamplesGsBugatti Veyron from 0 to 100 km/h in 2.4 s 1.18High-g roller coasters 3.5–6.3Top fuel drag racing world record of 4.4 s over1/4 mile4.2Sprint Missile 100Rating of electronics built into military artilleryshells15,500
Effects on Body• A normal healthy person would startexperience loss of vision at around 5-6 g• Roller coasters give forces of maximum up to3 to 4 gs for brief periods of time.• If a force of 4 to 6 gs is held for more than afew seconds, the results could bedevastating; such as blackouts to death.• The devastating car crash of Princess Dianaof Wales in 1997 was estimated to rangesomewhere between 70–100 gs. Thisaccident was intense enough to pull thepulmonary artery from her heart.
Simple Machines• A mechanical device that provides a change inforce 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 pullsobjects 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 objectmove.
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 anobject to a higher or lower place.
What is a Wedge?• A doorstop is a wedge.• A wedge is a simple machine used to pushobjects apart.• An ax is a wedge that splits wood.
What is a Screw?• A screw is a simple machine used to holdobjects together.• Think about your desk.• Does it have screws helping to hold ittogether?
What is a Wheel and Axle?• A wheel and axle is a simple machine made ofa rod attached to the center of a wheel.• The axle, or rod, turns when you put force onthe wheel.• You probably have seen a wheel and axle oncars, skateboards, etc.
What is a Pulley?• A pulley is a simple machine with a wheel andwith a rope.• The rope fits around the edge of the wheel.• You can use a pulley to move a load up, downor sideways.
Links• How Can I Help?• Simple Machines
What is a Catapult?• In modern times, the word catapult can beused to describe any machine that hurls aprojectile.• 3 Types– Onager– Ballista– Trebuchet
Onager• One Arm or Lever• Torsion Device– Twisted rope or rubberbands to create tension.• Gift from the Romans
Ballista• This machine was deliberatelyinvented by the Greeks,around 800 BCE.• Ballista were even mountedon warships and used to hurlfire onto other ships.• Functions similar to acrossbow or sling shot.
Trebuchet• The Trebuchet is probablythe oldest type of catapult.• It was invented either by theChinese or in the middleeast.• Trebuchets were used mainlyas lobbing machines tospread fire and diseasedcorpses, as well as a lot ofsolid missiles, over the wallsof castles to rain down onthe inhabitants.
Necessary ForcesSpeedInstant 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?
Speed equals distance divided by time.s=d/tSpeed
Force• Force is the push or pull exerted on an object.• The magnitude of a force can be found by multiplyingthe mass and the acceleration of the object.• Force equals mass times acceleration.
Shape• “Slippery” – theobject slipsthrough the air.• Air should glideover smoothly aswell as go under.• Even a mirror ordoor handle thatsticks out candetourperformance.
Drag• The faster an object travelsthe more the drag.• Drag can reduce speedbecause it will trace theoverall top of the car.• Any mistakes or areas thataren’t smooth will create adrag force.• Drag actually pushes in theopposite direction you wantto go.
Lift• Lift goes underneaththe car and pushedupward.• Lift can reduce speedby actually lifting thecar off the ground.
Friction• Force that opposesmotion.• This force comes fromthe axle rubbing the holethat was drilled for it.• To eliminate this takeyour pencil and “color”the axle.• Friction is often the forcethat brings objects torest.