IN MOTION PART 2 MR KECMAN CLASS 1

IN MOTION: PART 2 MR. KECMAN

CLASS 1 • Agenda • Learn about the history of force • Handout for Balloon Car Race • Video

PART 2: FORCE • • History of Motion Inertia in car collisions Forces Newton's laws Momentum and Impulse Friction Braking Distance

REMEMBER • Motion: • Defined as the process of the movement of an object from one place to another. • The study of the motion of objects and the forces that affect their motion is called Mechanics • Mechanics is divided up into: • Kinematics • Dynamics

DYNAMICS • Is the branch of mechanics dealing with motion of objects under the action of force. • Dynamics answers these questions: • Why is the object speeding up or slowing down? • How does it turn?

THE HISTORICAL DEVELOPMENT OF OUR IDEAS OF MOTION

WE WILL LOOK AT 3 SCIENTISTS FROM HISTORY • Aristotle • Galileo • Newton

Aristotle thought that heavier objects fell to the ground faster than lighter objects…. …and that all motion on the Earth was straight and linear. The way Aristotle thought projectiles moved. The way projectiles “really” move.

STRAIGHT AND LINEAR MOTION: The way Aristotle “saw” objects fall on the Earth. vacuum. As we know, or will know soon, objects actually fall like this in a friction-free environment

Because Aristotle was a very powerful man, his incorrect ideas were propagated for over 2000 years.

Galileo Galilei (15641642) performed many “thought experiments” with respect to motion. From these experiments, he proposed that the motion of a falling object does not depend on mass, but on friction.

Interestingly enough, it is the force of friction that stops an object. Forces aren’t actually required to keep an object in motion.

This is what Galileo would have seen at Pisa—two balls with unequal masses falling in the same time. (There would have been little wind on the day of Galileo's experiment, so friction would have been minimal) http: //www. youtube. com/w atch? v=5 C 5_d. OEy. Afk

MISCONCEPTIONS ABOUT FALLING OBJECTS https: //www. youtube. com/watch? v=_m. CC 68 Ly. ZM&spfreload=10

BRAINIACS—DO HEAVY OBJECTS FALL FASTER THAN LIGHT OBJECTS? ARISTOTLE VS. GALILEO http: //www. youtube. com/watch? v=AYz_K 3 mwq 6 A

In the absence of friction, a ball rolling down a ramp would theoretically continue moving until it reached its original height.

NOTE: It is the force of friction that stops an object. Forces aren’t actually required to keep an object in motion.

NEWTON’S 3 LAWS OF MOTION

FIRST LAW An object at rest will stay at rest, and an object in motion will stay in motion unless a force is applied to the object.

Tablecloth trick http: //www. youtube. com/watch? v=z. We. KRMh 3 k. T 8 How to perform the coin and card stunt http: //www. youtube. com/watch? v=np 53 X 9 MTKJo

AMAZING BOTTLE TRICKS - COOL SCIENCE EXPERIMENT http: //www. youtube. com/watch? v=c. BK 4 w. XT 3 Fo. I&feature= youtu. be

INERTIA The tendency of an object to resist changes in motion. Inertia http: //www. youtube. com/watch? v=7 LGi-Dlb 8 Vs

BALANCED VS. UNBALANC ED FORCES

APPLICATIONS OF THE FIRST LAW • Blood rushes from your head to your feet while quickly stopping when riding on a descending elevator. • The head of a hammer can be tightened onto the wooden handle by banging the bottom of the handle against a hard surface.

• To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrust downward at high speeds and then abruptly halted. • The ladder on the roof of a truck which stops abruptly breaks its harness straps and slides off the top of the vehicle, becoming a dangerous projectile.

• Headrests are placed in cars to prevent whiplash injuries during rear-end collisions. • While riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb or rock or other object which abruptly halts the motion of the skateboard.

SECOND LAW (AKA: F = MA) When a force is applied to an object, the object will accelerate in the direction of the force.

THIRD LAW For every action, there is an equal and opposite, reaction.

Giant Newton’s cradle http: //www. youtube. com/watch? v=m. FNe_p. FZrs. A Newton’s cradle applet http: //www. walter-fendt. de/ph 14 e/ncradle. htm

Stomp Rocket http: //www. youtube. com/watch? v=Pu_Xegh. O 6 WU&featu re=related http: //www. youtube. com/watch? v=i 5 XAu. Az_4 bs&feature =related

Three laws of motion: http: //www. youtube. com/watch? v=JGO _z. DWmkvk http: //www. youtube. com/watch? v=Pk. A O 8 F-Tm-w

CLASS 2 • Video • Balloon Car explanation

FORCE! • https: //www. youtube. com/watch? v=06 z. CLTSa. Pmc&spfr eload=10 • (Bill nye force) • Watch the video and answer the worksheet as best you can.

ANSWERS • 1. What puts things in motion? Forces • 2. Forces are like ______ or ______. (both letters start with the letter P) pushes, pulls • 3. When something is sitting still, it stays sitting still unless acted on by an ________. When something is moving it keeps moving unless acted on by an _________. Outside force (x 2)

ANSWERS • 4. “Harder to move” is a property of matter called _________ inertia • 5. Why does the quarter fall into the glass? (one word) inertia • 6. Things at rest stay at ______, things in motion stay in ______, unless acted on by an outside _______. Rest, motion, force • 7. F= ______ x __________ mass, acceleration

ANSWERS • 8. For every action, there is an equal and ________________ opposite reaction • 9. In zero gravity, do the Laws of Motion still apply? Yes • 10. Is the fire extinguisher in the room moving? Yes, everything is really moving since the earth is moving, but relative to the earth, no.

HAND OUT • Please stretch your legs and come pick up a Balloon Car Information Sheet

CLASS 3 • Agenda: • Complete the booklet and stations. • If you finish early, try the Force Worksheet. Do at home!

CLASS 4 • Agenda: • Refresh • Momentum and Impulse • WS

REFRESH • Aristotle • Linear motion and heavy objects faster • Galileo • Proved Aristotle was wrong • Newton • Developed 3 laws which are:

REFRESH • 1) object at rest will stay at rest, and an object in motion will stay in motion unless a force is applied to the object • 2) f = m x a • 3) For every action, there is an equal and opposite, reaction

MOMENTUM AND IMPULSE Remember that math is the language of the Universe! Newton actually formulated his Second Law in terms of the change in velocity. So, if F= ma, F= m Δv Δt If we cross-multiply, we end up with FΔt = mΔv

FΔT = MΔV On the left-hand side we are left with FΔt. The force applied over a certain period of time is called impulse. To increase impulse, we must increase the force applied, or the time over which we apply the force.

FΔT = MΔV On the right-hand side we are left with mΔv. The product of mass and the change in velocity is called momentum, and is known as a quantity of motion. For example, a 100, 000 kg train moving at 5. 0 m/s has more momentum than a 10 g Hot Wheels™ car moving at 5. 0 m/s. It is therefore more difficult to stop a moving train than a moving Hot Wheels™ car.

In order to change the momentum of an object, we must change its velocity (as we don’t want to change its mass) by applying an impulse. For example, to move a ball, we must apply a force on the ball over a certain period of time. http: //www. youtube. com/w atch? v=Ea. GUUc. BTanw

If the ball must move a greater distance, we may obtain greater momentum (velocity) either by increasing the force (by kicking, hitting, or throwing the ball harder) or by applying the force for a greater length of time (“following through”). http: //www. youtube. com/watch? v =l. BMA 2 w. Wuqh 8 http: //www. youtube. com/watch? v =Or. Lc. ZNG 0 N 0 I

On the other hand, to bring a moving object to rest, an impulse is required to reduce the momentum to zero. In a car collision, the impulse which is most threatening to drivers and passengers is called the “second collision. ” This occurs when the individual hits the steering wheel, windshield, or any other rigid object.

Since impulse is the product of FΔt, when a person collides with a fixed object, the duration of time is very small and the force is very large. The result is damage to the car and severe personal injury. • How do we prevent this?

To protect passengers in moving vehicles, engineers try to “cushion” the blow (reduce the force of the impact) by increasing the duration of time over which the force from the collision is applied before the momentum is reduced to zero.

Technologies that have been developed to cushion the impact of the second collision include seat belts and air bags.

STRETCHING VS NON STRETCHING SEATBELTS

Concussions are a common result of motor vehicle collisions http: //www. youtube. com/watch? v=f. Y 7 J 7 bcc. No. U

W. S. • Try to do the force worksheet I gave you yesterday and also this new one which mixes forces with momentum and impulse

CLASS 5 • Agenda: • RACE DAY!!!! • Hand out Questions/ Rubric

CLASS 6 • Agenda: • Conservation of momentum and impulse word doc • Time for impulse/momentum worksheet • Start conservation of energy

MOMENTUM AND IMPULSE • Word Doc

CONSERVATION OF ENERGY • Law of Conservation of Energy – • energy cannot be lost or created, but can only be transformed or converted into different forms of energy. • In a car collision, huge amounts of kinetic energy are converted and transferred to other systems. Energy can be converted to several different types of energy, such as:

CONSERVATION OF ENERGY • Kinetic energy: • the energy of motion (e. g. , wheels turning)

CONSERVATION OF ENERGY • Potential energy: • the energy of position with respect to the surface of the Earth (e. g. , an object falling from two storeys up will not fall with as much force or acceleration as an object that falls from 16 floors up)

CONSERVATION OF ENERGY • Heat energy: • the energy of molecules in motion (e. g. , smoke rising from an engine)

CONSERVATION OF ENERGY • Sound energy: • the disturbance of molecules (e. g. , a loud crashing sound)

• As the kinetic energy reduces to zero, other forms of energy increase.

CLASS 7 • Agenda: • Physics of a car crash • Video handout

UNDERSTANDING CAR CRASHES IT'S BASIC PHYSICS • https: //www. youtube. com/watch? v=y. Upi. V 2 I_IRI&spfreloa d=10

VIDEO ANSWERS • Why did the dummy get left behind? It’s called inertia , the property of matter that causes it to resist any change in its motion. • Isaac Newton’s circle one 1 st 2 nd 3 rd Law of Motion states: A body at rest remains at rest unless acted upon by an external force , and a body in motion continues to move at a constant speed in a straight line unless it is acted upon by an external force.

VIDEO ANSWERS • Crashing Dummies • Now watch what happens when the car crashes into a barrier. The front end of the car is crushing and absorbing energy which slows down the rest of the car. • In this case, it is the steering wheel and windshield that applies the force overcomes the dummy's inertia.

VIDEO ANSWERS • Crash-Barrier Chalkboard • Newton explained the relationship between crash forces and inertia in his circle one 1 st 2 nd 3 rd Law of Motion. • (Fill in the blanks to explain what each letter in the formula represents. )

VIDEO ANSWERS F= force F=ma m= mass a= acceleration F=m∆v/t ∆v= change in velocity t= time or rate Ft = impulse Ft = m∆v = change in momentum

VIDEO ANSWERS • Surfers, Cheetahs, and Elephants. . . oh my! Momentum is inertia in motion. It is the product of an object's mass and its velocity. • Which has more momentum? An 80, 000 pound big rig traveling 2 mph or a 4, 000 pound SUV traveling 40 mph? circle one: Big Rig SUV same

VIDEO ANSWERS • Soccer Kicks, Slap Shots, and Egg Toss What is it that changes an object's momentum? an impulse. It is the product of force and the time for which it acts. • If the eggs are of equal mass and are thrown at the same velocity they will have the same momenta. The wall and the sheet both apply equal impulses.

VIDEO ANSWERS • The wall applies a bigger force over a shorter time, while the sheet applies a smaller force over a longer time. • With panic braking the driver stops in less time or distance and experiences more force.

VIDEO ANSWERS • Crashing and Smashing • The second animated vehicle’s front end is less stiff so it crushes two feet instead of one, causing the deceleration to decrease from 30 gs to 15 gs. • Extending the time of impact is the basis for many of the ideas about keeping people safe in crashes. List three applications in vehicle or highway safety. • 1. crumple zones 2. airbags 3. break-away light poles

VIDEO ANSWERS • Conserving Momentum and Energy - It’s the Law! • In a collision of two cars of unequal mass, the occupants of the lighter car would experience much higher accelerations , hence much higher forces than the occupants of the heavier car. • Motion related energy is called kinetic energy. Energy due to an object’s position or conditions is called potential energy.

VIDEO ANSWERS • At what point in the pendulum's swing is its potential energy equal to its kinetic energy? mid-point When is its kinetic energy at its maximum? bottom • Circle the correct formula for kinetic energy (KE). • KE = 1/2 m 2 v • KE = 1/2 2 mv 2 • KE = 1/2 mv 2

GROUP TIME • Pick up the handout and as a group come up with an answer for the 1 question. • Present it to the class.

CLASS 8 • Agenda: • Possible presentations of group work • Braking Distance

EFFECTS OF BREAKING DISTANCE • Word Doc

CLASS 9 • Agenda: • Lab on: • Total stopping distance • Friction • Breaking Distance • Reaction Time

CLASS 10 • Agenda: • Review day • Complete the rest of your Glossary • Try to complete the unit outline questions

CLASS 11 • Agenda: • TEST!

CLASS 12 • UN Egg drop.