Roller Coaster Physics Dynamics z Why things move

Roller Coaster Physics

Dynamics z. Why things move y. Accelerations caused by Forces

Forces Non Contact Gravitational Electromagnetic Contact Nuclear Pushes Pulls W Electric Magnetic Normal M N perpendicular to surface Friction f Tension T

Labeling Forces What forces are acting on the yellow ball? F

Labeling Forces What forces are acting on the yellow ball? Fby, on

Labeling Forces What forces are acting on the yellow ball? Wby, on

Labeling Forces What forces are acting on the yellow ball? WEarth, Ball

Labeling Forces Fby, on ANYTHING LESS IS AN INCOMPLETE ANSWER!!!

Sir Isaac Newton (1642 -1727)

Newton’s Laws of Motion z 1 st Law: • no net force no acceleration • no acceleration no change in motion • Objects at rest will remain at rest and objects in motion will remain in motion at constant speed, in a straight line, unless acted on by a net force

Newton’s Laws of Motion z 1 st Law: • no net force no acceleration • no acceleration no change in motion • Objects at rest will remain at rest and objects in motion will remain in motion at constant speed, in a straight line, unless acted on by a net force

Mass z. Measure of how much ‘stuff’ z. Measure of how hard it is to speed up or slow down the object z. Mass and weight are very different

POP!

More net force - more acceleration (constant mass) a Fnet F a

More mass - less acceleration (constant net force) 1 a M F a

Putting it all together Fnet a M Fnet a Constant * M Newton is defined such that constant = 1. Fnet M a Newton’s 2 nd Law

Newton’s Laws z 1 st y. Objects at rest will stay at rest and objects in motion will stay in motion, at a constant speed, in a straight line, unless acted on by a net force. z 2 nd y. Objects with a non-zero net force accelerate in the direction of the net force via Fnet = ma

THE BRICK OF DEATH!!! I Physics

• What THING is pushing on the rocket? • Is this a contact or non-contact force?

Poor Gary: Gary has a major problem. After studying Newton’s Third Law in his physics class, he has convinced himself of its validity. Unfortunately, he has convinced himself while sitting in a closed room with a single door. He reasons to himself: “If I push on the door to go out, Newton’s 3 rd Law tells me that the door is going to push back with an equal force. That force is going to cancel the force that I push with. Even if I push as hard as I can, that door is going to push back just as hard! Oh no! I’m stuck in this room! Why did I ever take physics!”

The famous bug problem: • A bug splats on the windshield of a car moving at 100 mph. Which feels the greater force, the car or the bug? • Which has the worst day?

Newton’s 3 rd Law and the Scale Apparent Weight NFS NSP person True Weight WEP scale WES NPS

Apparent weight • measured as the reading of the scale • equal to the normal force of the scale on your feet • equal to weight for a=0

Elevator v = constant Apparent Weight NSP a=0 True Weight WEP

Elevator a is upward Apparent Weight NSP a True Weight WEP

Elevator a is downward Apparent Weight NSP a True Weight WEP

Elevator a =9. 8 m/s/s down How large should the normal force be? NSP g WEP

Elevator a =9. 8 m/s/s down g How large should the normal force be? Apparently Weightless? ? WEP

The weightlessness of space!

What’s his mass? 80 kg

What’s his weight? 648 N ! What ?

Apollo 17 Earth as seen from the Moon

What is the correct orbit of the space shuttle?

What is the correct orbit of the space shuttle?

a = 8. 1 m/s 2

Orbit z“…there is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss. ” – Douglas Adams Life, The Universe, and Everything

Circular motion Which direction is the instantaneous velocity?

Uniform Circular motion Which direction is the instantaneous velocity? Which direction is the acceleration?

Uniform Circular motion Which direction is the instantaneous velocity? Which direction is the acceleration? TS, B Freebody WE, B

Uniform Circular motion Which direction is the instantaneous velocity? Which direction is the acceleration? TS, B Freebody WE, B

Uniform Circular motion Which direction is the instantaneous velocity? Which direction is the acceleration? Ty Freebody Tx WE, B Aren’t we missing something?

THE CENTRIFUGAL FORCE! z. Centrifugal. adj. Moving or directed away from the center. Ty Tx WE, B

THE CENTRIFUGAL CENSORED FORCE! CENSORED adj. Moving or directed away from z. Centrifugal. the center. Ty Tx WE, B

Forces Non Contact Gravitational Electromagnetic Contact Nuclear Pushes Pulls W Electric Magnetic Normal M N perpendicular to surface Friction f Tension T

THE CENTRIFUGAL CENSORED FORCE! CENSORED adj. Moving or directed away from z. Centrifugal. the center. z. The centri*&%#l force DOES NOT EXIST! z. For uniform circular motion the net force T must be towards the center of the circle. y z. Therefore: The acceleration is ‘center Tseeking’ x WE, B

THE CENTRIFUGAL CENSORED FORCE! CENSORED adj. Moving or directed away from z. Centrifugal. the center. z. The centri*&%#l force DOES NOT EXIST! z. For uniform circular motion the net force T must be towards the center of the circle. y z. Therefore: The acceleration is centripetal Tx WE, B

The swinging bucket of death C I Physics Draw freebody diagrams for the water at points A, B, and C. B A

Centripetal Acceleration z. For U. C. M. there must be a centripetal net force

Centripetal Acceleration z. For U. C. M. there must be a centripetal net force centripetal acceleration