Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the...
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Transcript of Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the...
![Page 1: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/1.jpg)
Momentum and Energy
PHYS 1090 Unit 3
![Page 2: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/2.jpg)
Question
If a car collides with a bug, which experiences the greatest force?
A. The car.
B. The bug.
C. It’s a tie.
D. Insufficient information to answer.
![Page 3: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/3.jpg)
Force Meters
![Page 4: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/4.jpg)
Newton’s Third Law
• Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first, along the same line of interaction.
• To every action there is always an opposed equal reaction.
• If object A exerts force F on object B, object B exerts force –F on object A.
FA→B = −FB→A
![Page 5: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/5.jpg)
Bug + Windshield
Small car: 1250 kg
From the same force, the bug accelerates a lot more!
Large insect: 0.00025 kg
Forces are the same—the accelerations are different.
![Page 6: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/6.jpg)
Interaction Forces
All forces are interaction forces!– gravity– wind– jumping– everything!
• This means: whenever something accelerates, something else accelerates in the opposite direction! Whoa!
![Page 7: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/7.jpg)
Pulleys
![Page 8: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/8.jpg)
Pulleys
• Change the direction but not magnitude of the tension in the cable
• Lift force is tension times number of segments lifting
• Lift height is pull divided by number of segments
![Page 9: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/9.jpg)
Levers
![Page 10: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/10.jpg)
Levers
• To balance a load, the force closest to the fulcrum must be larger
![Page 11: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/11.jpg)
Levers
• To balance a load, the force closest to the fulcrum must be larger
• The load farthest from the fulcrum moves the most
![Page 12: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/12.jpg)
Inclined Planes
![Page 13: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/13.jpg)
Inclined Planes
• The steeper the plane, the greater the force required
• The steeper the plane, the shorter the distance pulled to reach the same height
![Page 14: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/14.jpg)
Simple Machines
• All are a trade-off between force and distance (or force and speed)
• The greater force moves the least distance
F1d1 = F2d2
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Work
Formula
work = F·d
F = force appliedd = distance traveled
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Simple Machines
F1d1 = F2d2
Work input = Work output
• Forces are different
• Distances are different
• Work is the same.
![Page 17: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/17.jpg)
Work and Energy
• Doing work on something changes its energy.
• Energy: “the ability to do work”
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Conservation of Energy
• Energy can be transferred between objects or transformed into different forms, but the total amount of energy can never change.
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Rail Cart Collisions
![Page 20: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/20.jpg)
Rail Cart Collisions
• Accelerations are in opposite directions
• More massive cart accelerates the least
• Equal-mass carts have equal accelerations (in opposite directions)
• Total Mass·Velocity the same before and after collisions
![Page 21: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/21.jpg)
Air Hockey Collisions
![Page 22: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/22.jpg)
Air Hockey Collisions
• Accelerations are in opposite directions
• More massive disk accelerates the least
![Page 23: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/23.jpg)
Momentum
• “Inertia in motion”
• Massive objects are hard to get going.
• Massive objects are hard to stop.• It is hard to give an object a high speed.• It is hard to stop a high-speed object.
![Page 24: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/24.jpg)
Momentum
Formula
momentum is a vector.
p = mv
![Page 25: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/25.jpg)
Momentum Changes and Newton’s Third Law
• At any instant:
p = (mv) = mv = mat = m(F/m)t = Ft
• For interacting objects, FA = −FB, so:
pA = FAt
pB = FBt = −FAt
pA = −pB
![Page 26: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/26.jpg)
Conservation of Momentum
• Momentum can be transferred between objects, but the total momentum can never change.
p1 + p2 = 0
![Page 27: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/27.jpg)
Rollerballs and Drag Meters
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Rollerballs and Drag Meters
• The lighter the meter, the farther it drags.• The heavier the ball, the farther it drags a meter.• The higher the ramp, the farther a ball drags a
meter.• The higher the ramp, the faster a ball rolls at the
bottom.• The mass of the ball has no influence on how
fast it rolls at the bottom.
![Page 29: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/29.jpg)
Some Forms of Energy
• Potential Energy
• Kinetic energy
![Page 30: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/30.jpg)
Work Against Gravity
Force = –w = mg
distance = h
work = mgh
Source: Griffith, The Physics of Everyday Phenomena
![Page 31: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/31.jpg)
Get It Back?
Gravity exerts force mg as object drops distance h.
work = mgh
Source: Griffith, The Physics of Everyday Phenomena
![Page 32: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/32.jpg)
Potential Energy
The energy of relative position of two objects
gravity
springs
electric charges
chemical bonds
![Page 33: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/33.jpg)
Potential Energy
Gravitational potential energy =
the work done by gravity in lowering an object
– or –
the work to raise an object to a height
Gravitational PE = mgh
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A Moving Object Can Do Work
Source: Griffith, The Physics of Everyday Phenomena
![Page 35: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/35.jpg)
Kinetic Energy
the work that a moving object does in stopping
– or –
the work to bring a motionless object to speed
KE = 12 mv2
![Page 36: Momentum and Energy PHYS 1090 Unit 3. Question If a car collides with a bug, which experiences the greatest force? A.The car. B.The bug. C.It’s a tie.](https://reader030.fdocuments.in/reader030/viewer/2022032702/56649ccc5503460f949961c7/html5/thumbnails/36.jpg)
Rollerball Energy Conversions
work
Potential energy
Kinetic energy
work
The more work you put in, the more work you get out!