Work And Power
Overview
Two students carry identical boxes of books up the same staircase. One runs and arrives out of breath in 8 seconds; the other strolls up in 40. They have done exactly the same amount of work, and they are nowhere near equally powerful. That distinction is the heart of this topic.
Here you will meet the equation for work done, the two energy equations that go with it for height and for speed, the conservation rule that ties all three together, and the definition of power that separates how much energy from how quickly.
Objectives
- Know and use the relationship between work done, force and distance moved in the direction of the force: W = F x d
- Know that work done is equal to energy transferred
- Know and use the relationship between gravitational potential energy, mass, gravitational field strength and height: GPE = m x g x h
- Know and use the relationship: kinetic energy = 0.5 x mass x speed squared
- Understand how conservation of energy produces a link between gravitational potential energy, kinetic energy and work
- Describe power as the rate of transfer of energy or the rate of doing work
- Use the relationship between power, work done (energy transferred) and time taken: P = W/t
Mind map
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Flashcards
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Work And Power. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Work done is calculated using: A) force x time B) force x distance moved in the direction of the force C) force / distance D) mass x speed Answer: B
- A force of 30 N moves a box 5 m in the direction of the force. The work done is: A) 6 J B) 35 J C) 150 J D) 900 J Answer: C
- If the speed of an object doubles, its kinetic energy: A) stays the same B) doubles C) is four times greater D) is halved Answer: C
- Power is defined as: A) the total energy transferred B) force x distance C) the rate of transfer of energy D) energy x time Answer: C
- A machine does 6000 J of work in 30 s. Its power is: A) 20 W B) 200 W C) 2000 W D) 180000 W Answer: B
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Practice Mock Questions
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