Roller Coaster Physics
description
Transcript of Roller Coaster Physics
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Dynamics
Why things move Accelerations caused by Forces
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Forces
Non Contact Contact
Pushes PullsGravitational Electromagnetic Nuclear
Normal Friction Tension
M T f N
WElectric Magnetic
perpendicular to surface
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Labeling Forces
What forces are acting on the yellow ball?
F
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Labeling Forces
What forces are acting on the yellow ball?
Fby, on
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Labeling Forces
What forces are acting on the yellow ball?
Wby, on
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Labeling Forces
What forces are acting on the yellow ball?
WEarth, Ball
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Labeling Forces
Fby, onANYTHING LESS IS AN INCOMPLETE ANSWER!!!
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Sir IsaacNewton
(1642-1727)
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Newton’s Laws of Motion
1st 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
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Newton’s Laws of Motion
1st 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
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Mass
Measure of how much ‘stuff’
Measure of how hard it is to speed up or slow down the object
Mass and weight are very different
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POP!
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More net force - more acceleration(constant mass)
F
a
F
a
a Fnet
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More mass - less acceleration(constant net force)
F
a
a
F
a M1
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Putting it all together
a MFnet
Constant *
Newton is defined such that constant = 1.
a MFnet
aMFnet
Newton’s 2nd Law
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Newton’s Laws
1st
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.
2nd
Objects with a non-zero net force accelerate in the direction of the net force via Fnet = ma
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THE BRICK OF DEATH!!!
I
Physics
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•What THING is pushing on the rocket?
•Is this a contact or non-contact force?
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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 3rd 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!”
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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?
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WEP
NSP
person
NFS
WES
NPS
scale
Apparent Weight
True Weight
Newton’s 3rd Law and the Scale
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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
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Elevator
WEP
NSP
v = constant
a = 0
Apparent Weight
True Weight
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Elevator
WEP
NSP
a is upward
a
Apparent Weight
True Weight
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Elevator
WEP
NSP
a is downward
a
Apparent Weight
True Weight
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Elevator
WEP
NSP
How large should the normal force be?a =9.8 m/s/s down
g
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Elevator
WEP
a =9.8 m/s/s down
How large should the normal force be?
g Weightless??Apparently
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The weightlessness of space!
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What’s his mass?
80 kg
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What’s his weight?
648 N !
What ?
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Apollo 17
Earth as seen from the Moon
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What is the correct orbit of the space shuttle?
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What is the correct orbit of the space shuttle?
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a = 8.1 m/s2
a = 8.1 m/s2
a = 8.1 m/s2
a = 8.1 m/s2
a = 8.1 m/s2
a = 8.1 m/s2
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Orbit
“…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 AdamsLife, The Universe, and Everything
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Circular motion
Which direction is the instantaneous velocity?
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Uniform Circular motion
Which direction is the instantaneous velocity?
Which direction is the acceleration?
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Uniform Circular motion
WE,B
TS,B
Freebody
Which direction is the instantaneous velocity?
Which direction is the acceleration?
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Uniform Circular motion
Which direction is the instantaneous velocity?
Which direction is the acceleration?
WE,B
TS,B
Freebody
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Uniform Circular motion
Which direction is the instantaneous velocity?
Which direction is the acceleration?
Freebody
Aren’t we missing something?
Ty
WE,BTx
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THE CENTRIFUGAL FORCE!
Centrifugal. adj. Moving or directed away from the center.
Ty
WE,BTx
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THE CENTRIFUGAL FORCE!CENSORED
Centrifugal. adj. Moving or directed away from the center.
Ty
WE,BTx
CENSORED
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Forces
Non Contact Contact
Pushes PullsGravitational Electromagnetic Nuclear
Normal Friction Tension
M T f N
WElectric Magnetic
perpendicular to surface
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Ty
WE,BTx
THE CENTRIFUGAL FORCE!CENSORED
Centrifugal. adj. Moving or directed away from the center.
The centri*&%#l force DOES NOT EXIST!For uniform circular motion the net force
must be towards the center of the circle.Therefore: The acceleration is ‘center
seeking’
CENSORED
CENSORED
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Ty
WE,BTx
THE CENTRIFUGAL FORCE!CENSORED
Centrifugal. adj. Moving or directed away from the center.
The centri*&%#l force DOES NOT EXIST!For uniform circular motion the net force
must be towards the center of the circle.Therefore: The acceleration is
centripetal
CENSORED
CENSORED
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The swinging bucket of death
A
B
CI
Physics
Draw freebody diagrams for the water at points A, B, and C.
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Centripetal Acceleration
For U.C.M. there must be a centripetal net force
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Centripetal Acceleration
For U.C.M. there must be a centripetal net force centripetal acceleration