Lesson 1: Work Done by a Constant Force
Overview:
In this lesson you will explore the conditions required for work to be done, that is work in the physics sense.
Curriculum Expectations:
Overall Expectations:
C3. Demonstrate an understanding of work, energy, momentum, and the laws of conservation of energy and conservation of momentum, in one and two dimensions.
Specific Expectations:
C2.1 Use appropriate terminology related to energy and momentum, including, but not limited to:
work, work–energy theorem, kinetic energy, gravitational potential energy, elastic potential energy, thermal energy, impulse, change in momentum–impulse theorem, elastic collision, and inelastic collision.
C2.3 Use an inquiry process to analyse, in qualitative and quantitative terms, situations involving work, gravitational potential energy, kinetic energy, thermal energy, and elastic potential energy, in one and two dimensions (e.g., a block sliding along an inclined plane with friction; a cart rising and falling on a roller coaster track; an object, such as a mass attached to a spring pendulum, that undergoes simple harmonic motion), and use the law of conservation of energy to solve related problems.
C3. Demonstrate an understanding of work, energy, momentum, and the laws of conservation of energy and conservation of momentum, in one and two dimensions.
Specific Expectations:
C2.1 Use appropriate terminology related to energy and momentum, including, but not limited to:
work, work–energy theorem, kinetic energy, gravitational potential energy, elastic potential energy, thermal energy, impulse, change in momentum–impulse theorem, elastic collision, and inelastic collision.
C2.3 Use an inquiry process to analyse, in qualitative and quantitative terms, situations involving work, gravitational potential energy, kinetic energy, thermal energy, and elastic potential energy, in one and two dimensions (e.g., a block sliding along an inclined plane with friction; a cart rising and falling on a roller coaster track; an object, such as a mass attached to a spring pendulum, that undergoes simple harmonic motion), and use the law of conservation of energy to solve related problems.
Success Criteria:
- Define the physics idea of doing work.
- Is work a scalar or vector quantity?
- What is the effect of negative work on the kinetic energy of an object?
- For what angle range is the force acting on an object doing (i) positive work and (ii) negative work.
- Describe the three situations in which zero work is done by a force on an object.
- In uniform circular motion is the force that provides the centripetal force doing work on the object?
Time Allocation: 1 hour
Learning Activities:
Read pages 164 - 169 from Nelson 4.1 and copy the sample problems into your notes.
In the playlist below, video:
- Will explain the basic concept of work, energy, and power.
- Will show you how to find the work done by pushing a box at an angle.
- Will show you how to find the work done by a person walking carrying a box.
Practice questions 1, 2, and 3 on page 166.
Practice questions 1, 2, and 3 on page 167.
Practice question 1 on page 168.
Practice question 1 on page 169.
Practice questions 1, 2, and 3 on page 167.
Practice question 1 on page 168.
Practice question 1 on page 169.
Task:
Solve questions 1 and 4 from Nelson 4.1 Review on page 170.
Optional Extension:
Optional Extension:
- Solve questions 5 and 6 on page 170.
Reflect:
A toy consists of a small plastic tube connected at the centre to one end of a long string. A girl holds the other end of the string and swings the toy in a horizontal, circular path above her head. Is work done on the toy by the string during each revolution? Explain your reasoning.
Additional Resources:
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Will explain the products of vectors, or dot product, or scalar product.
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Will show you how to calculate the dot product of 2 vectors, example 1.
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Will show you how to calculate the dot product of 2 vectors, example 2.
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