chapter 7 energy introduction universe is made up of matter and energy. energy is the mover of...
TRANSCRIPT
![Page 1: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/1.jpg)
Chapter 7
Energy
![Page 2: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/2.jpg)
Introduction
• Universe is made up of matter and energy.
• Energy is the mover of matter.• It has several forms. To
understand this concept we will begin with a closely related physical concept.
![Page 3: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/3.jpg)
1. WORK
Now instead of a force for how long in time we consider a force for how long in distance.
Work = Force x distance or W = F.d Units - Joules (J) or ft.lb BTU = 778 ft.lb (energy of one wooden
kitchen match) Pushing on a wall and wall doesn’t move
(no work done on the wall)
![Page 4: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/4.jpg)
x
F
xFW x
xF
yF
![Page 5: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/5.jpg)
Video ClipVideo Clip
Manpowered MachinesManpowered Machines
![Page 6: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/6.jpg)
2. POWER
Power = Work/time or P = W/t
Units - J/s = W 550 ft.lb /s = 1 hp
1 hp = 746 J/s = 746 W
1 BTU/hr = 0.293 W
100 W bulb = 0.1341 hp
250 hp engine = 186,450 W
![Page 7: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/7.jpg)
3. MECHANICAL ENERGY
When work is done on an object, the object generally has acquired the ability to do work.
This is called energy and it has the same units as work.
Two Types of Mechanical EnergyPotential EnergyKinetic Energy
![Page 8: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/8.jpg)
Potential Energy
Energy of position or configuration
Demo - Dart gunDemo - Dart gun
Other examples - Springs, bow, sling shot,
chemical energy, and gravitational potential
energy
The latter is GPE = mgh
![Page 9: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/9.jpg)
The potential energy of an object depends
on a reference position.
It represents the work done against gravity
to put the mass m in its position h above
some reference position.
It is an energy of position.
![Page 10: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/10.jpg)
Video ClipsVideo Clips
InclineIncline
ScrewScrew
![Page 11: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/11.jpg)
Kinetic Energy
It is an energy of motion.
KE mv 12
2
It is a square law. Total Work (work done by all forces acting
on mass m) = KE
![Page 12: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/12.jpg)
221 )2( ivm
Work to Stop KE
)(4 221
imv
xFmvmv xif 2212
21
xFmv xi 221
0
221 4 ivm xxF
Note
![Page 13: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/13.jpg)
Work-Energy Theorem
The net work done on an object is equal to the change in the kinetic energy of the object.
Net Work = KE
![Page 14: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/14.jpg)
4. CONSERVATION OF ENERGY
Demo - Bowling ball pendulumDemo - Bowling ball pendulum
Demo - Loop the loopDemo - Loop the loop
Video - Pole VaultingVideo - Pole Vaulting
Galileo's inclines
Energy lost due to friction is actually not a
loss; it is just a conversion.
![Page 15: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/15.jpg)
Energy cannot be created or destroyed.
It may be transformed from one form into
another, but the total amount of energy
never changes.
Energy Conservation in Satellite Motion (Next slide)
![Page 16: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/16.jpg)
Ellipse
Ellipse
ParabolaH
yperbola
Energy is conserved alongall of these paths.
Perigees
Apogees
Circle
![Page 17: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/17.jpg)
Video ClipsVideo Clips
Driving NailsDriving Nails
Water WheelWater Wheel
Roller CoasterRoller Coaster
![Page 18: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/18.jpg)
Condition for Conservation of Mechanical Energy
No work can be done on the object by a
nonconservative force.
A nonconservative force is a force that
converts mechanical energy into another form.
Example: Friction
![Page 19: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/19.jpg)
No work is required to maintain circular
motion at constant speed.
![Page 20: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/20.jpg)
2mcE
![Page 21: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/21.jpg)
5. Machines
If no losses then
work input = work output
(F.d)input = (F.d)output
Examples - levers, block and tackle, etc. Demo - Block and tackle Demo - Block and tackle
Demo - Hydraulic liftDemo - Hydraulic lift
![Page 22: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/22.jpg)
FD = FD
D D
![Page 23: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/23.jpg)
6. EFFICIENCY
Efficiency = work done/energy used Useful energy becomes wasted energy with
inefficiency. Heat is the graveyard of useful energy. EER = energy efficiency ratio
It is the output capacity(BTU/hr)/input energy(Watts)
(Output capacity represents energy moved.)
![Page 24: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/24.jpg)
7. COMPARISON OF KINETIC ENERGY AND MOMENTUM
KE is a scalar and cannot be canceled.
![Page 25: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/25.jpg)
ip
0fp
I
Thief absorbs all the kinetic energy.
if ppp
This is the impulse applied to the bullet.
This is the impulse applied to the man.
![Page 26: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/26.jpg)
ip
Thief does not absorb all the kinetic energy.
fp ip
-
I
if ppp
This is the impulse applied to the bullet.
This is the impulse applied to the man.This is the impulse from previous slide.
![Page 27: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/27.jpg)
Rubber bullets versus lead bullets Slow and fast football players with different
masses. Consider head-on with one having twice the mass but half the speed of the other.
![Page 28: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/28.jpg)
![Page 29: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/29.jpg)
![Page 30: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/30.jpg)
0)2()2( vmvm
Twice the mass at half the speed. Momentum can cancel.
![Page 31: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/31.jpg)
2mv21 )2(
21 vmKE
22 )2(
21 vmKE
Kinetic energy is not a vector and cannot cancel out. The kinetic energy of the big slow person is
The kinetic energy of the small fast person is
22mv
![Page 32: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/32.jpg)
Punch is the same
but the energy delivered is not.
![Page 33: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/33.jpg)
8. SOURCES OF ENERGY
Except for nuclear and geothermal power, the source of practically all our energy is the sun.
Nuclear power
Geothermal power
Solar power
Wind power
![Page 34: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/34.jpg)
9. ENERGY FOR LIFE
Reading assignment
![Page 35: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/35.jpg)
Chapter 7 Review Questions
![Page 36: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/36.jpg)
A 10 lb weight is lifted 5 ft. A 20 lb weight is lifted 2.5 ft. Which lifting required the most work?
(a) 10 lb weight
(b) 20 lb weight
(c) same work for each lifting
(d) not enough information is given to work the problem
(c) same work for each lifting
![Page 37: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/37.jpg)
Two cars, A and B, travel as fast as they can to the top of a hill. If their masses are equal and they start at the same time, which one does the most work if A gets to the top first?
(a) A
(b) B
(c) they do the same amount of work
(c) they do the same amount of work
![Page 38: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/38.jpg)
An object of mass 6 kg is traveling at a velocity of 30 m/s. How much total work was required to obtain this velocity starting from a position of rest?
(a) 180 Joules
(b) 2700 Joules
(c) 36 Joules
(d) 5 Joules
(e) 180 N
(b) 2700 Joules
![Page 39: Chapter 7 Energy Introduction Universe is made up of matter and energy. Energy is the mover of matter. It has several forms. To understand this concept](https://reader036.vdocuments.net/reader036/viewer/2022062713/56649f535503460f94c77a88/html5/thumbnails/39.jpg)
A 20 pound weight is lifted 4 feet. The change in potential energy of the weight inft.lb is(a) 20
(b) 24
(c) 16
(d) 80
(e) 5
(d) 80