chapter 7 work and kinetic energy. units of chapter 7 work done by a constant force kinetic energy...
TRANSCRIPT
![Page 1: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/1.jpg)
Chapter 7
Work and Kinetic Energy
![Page 2: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/2.jpg)
Units of Chapter 7
• Work Done by a Constant Force
• Kinetic Energy and the Work-Energy Theorem
• Work Done by a Variable Force
• Power
![Page 3: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/3.jpg)
7-1 Work Done by a Constant Force
The definition of work, when the force is parallel to the displacement:
(7-1)
SI unit: newton-meter (N·m) = joule, J
![Page 4: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/4.jpg)
7-1 Work Done by a Constant Force
![Page 5: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/5.jpg)
7-1 Work Done by a Constant Force
If the force is at an angle to the displacement:
(7-3)
![Page 6: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/6.jpg)
7-1 Work Done by a Constant ForceThe work can also be written as the dot product of the force and the displacement:
![Page 7: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/7.jpg)
7-1 Work Done by a Constant Force
The work done may be positive, zero, or negative, depending on the angle between the force and the displacement:
![Page 8: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/8.jpg)
7-1 Work Done by a Constant Force
If there is more than one force acting on an object, we can find the work done by each force, and also the work done by the net force:
(7-5)
![Page 9: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/9.jpg)
7-2 Kinetic Energy and the Work-Energy Theorem
When positive work is done on an object, its speed increases; when negative work is done, its speed decreases.
![Page 10: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/10.jpg)
7-2 Kinetic Energy and the Work-Energy Theorem
After algebraic manipulations of the equations of motion, we find:
Therefore, we define the kinetic energy:
(7-6)
![Page 11: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/11.jpg)
7-2 Kinetic Energy and the Work-Energy Theorem
Work-Energy Theorem: The total work done on an object is equal to its change in kinetic energy.
(7-7)
![Page 12: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/12.jpg)
7-3 Work Done by a Variable Force
If the force is constant, we can interpret the work done graphically:
![Page 13: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/13.jpg)
7-3 Work Done by a Variable Force
If the force takes on several successive constant values:
![Page 14: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/14.jpg)
7-3 Work Done by a Variable Force
We can then approximate a continuously varying force by a succession of constant values.
![Page 15: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/15.jpg)
7-3 Work Done by a Variable Force
The force needed to stretch a spring an amount x is F = kx.
Therefore, the work done in stretching the spring is
(7-8)
![Page 16: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/16.jpg)
7-4 Power
Power is a measure of the rate at which work is done:
(7-10)
SI unit: J/s = watt, W
1 horsepower = 1 hp = 746 W
![Page 17: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/17.jpg)
7-4 Power
![Page 18: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/18.jpg)
7-4 Power
If an object is moving at a constant speed in the face of friction, gravity, air resistance, and so forth, the power exerted by the driving force can be written:
(7-13)
![Page 19: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/19.jpg)
Summary of Chapter 7
• If the force is constant and parallel to the displacement, work is force times distance
• If the force is not parallel to the displacement,
• The total work is the work done by the net force:
![Page 20: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/20.jpg)
Summary of Chapter 7
• SI unit of work: the joule, J
• Total work is equal to the change in kinetic energy:
where
![Page 21: Chapter 7 Work and Kinetic Energy. Units of Chapter 7 Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable](https://reader035.vdocument.in/reader035/viewer/2022062321/56649dac5503460f94a9be68/html5/thumbnails/21.jpg)
Summary of Chapter 7
• Work done by a spring force:
• Power is the rate at which work is done:
• SI unit of power: the watt, W