Work And Power
Aperçu
Lifting a suitcase, kicking a ball, climbing a hill: every one of these actions involves a force moving through a distance, and every one transfers energy from one store to another. The physics behind them centres on three tightly connected quantities: work, energy and power.
In this lesson you will learn how to calculate work done by a force, gravitational potential energy for an object at height, and kinetic energy for a moving object. You will see how conservation of energy links these stores together, and finish with power, the rate at which energy is transferred. These equations appear on almost every Edexcel Paper 1 sitting.
Objectifs
- Know and use the relationship between work done, force and distance moved in the direction of the force: work done = force x distance moved, 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 = 1/2 x mass x speed2, KE = 1/2 x m x v2
- 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: power = work done / time taken, P = W / t
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Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur Work And Power. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à l'épreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- A force of 50 N pushes a box 4 m across a floor. How much work is done? A) 12.5 J B) 54 J C) 200 J D) 800 J Answer: C
- A 3 kg object is lifted 5 m above the ground (g = 10 N/kg). What is its gravitational potential energy? A) 15 J B) 50 J C) 150 J D) 300 J Answer: C
- A ball of mass 0.2 kg travels at 10 m/s. What is its kinetic energy? A) 1 J B) 2 J C) 10 J D) 20 J Answer: C
- An object falls freely from rest. As it falls, which statement is correct (ignoring air resistance)? A) Its total energy increases B) Its GPE increases and KE decreases C) Its GPE decreases and KE increases by the same amount D) Its KE stays the same Answer: C
- A motor does 6000 J of work in 30 seconds. What is its power? A) 20 W B) 200 W C) 180 000 W D) 6030 W Answer: B
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Livres recommandés
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Section de manuel
Work: The Scientific Definition
The scientific definition of work differs in some ways from its everyday meaning. Certain things we think of as hard work, such as writing an exam or carrying a heavy load on level ground, are not work as defined by a scientist. The scientific definition of work reveals its relationship to energy—wh
"College Physics: Work: The Scientific Definition" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/7-1-work-the-scientific-definition. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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Section de manuel
Gravitational Potential Energy
Climbing stairs and lifting objects is work in both the scientific and everyday sense—it is work done against the gravitational force. When there is work, there is a transformation of energy. The work done against the gravitational force goes into an important form of stored energy that we will expl
"College Physics: Gravitational Potential Energy" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/7-3-gravitational-potential-energy. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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