Physics Work and Energy Concepts
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Questions and Answers

What is the scientific definition of work?

Work is done when a force makes something move.

What is the SI unit of work?

The SI unit of work is the joule (J).

How is work calculated?

Work is calculated using the equation: Work Done = Force × Distance Moved.

What does energy represent in scientific terms?

<p>Energy represents the capacity to do work.</p> Signup and view all the answers

What type of energy is associated with a moving object?

<p>Kinetic energy is associated with moving objects.</p> Signup and view all the answers

What energy store is involved when an object is lifted against gravity?

<p>Gravitational potential energy is involved when lifting an object against gravity.</p> Signup and view all the answers

What type of energy is stored in materials due to their atomic bonds?

<p>Chemical energy is stored in the bonds between atoms.</p> Signup and view all the answers

What energy store is created by electric charges that attract but are held apart?

<p>Electrostatic energy is created by electric charges that attract each other but are held apart.</p> Signup and view all the answers

What happens to the energy of a brick as it falls to the ground?

<p>The potential energy decreases while kinetic energy increases until all potential energy is converted to kinetic energy right before it strikes the ground.</p> Signup and view all the answers

What are the four pathways through which energy can be transferred?

<p>Energy can be transferred mechanically, electrically, by heating, and by radiation.</p> Signup and view all the answers

Explain how thermal energy is related to internal energy in materials.

<p>Thermal energy is the energy stored due to the motion of particles, which is a component of a material's internal energy.</p> Signup and view all the answers

What is the equation that relates work done and energy transferred?

<p>The equation is $Work Done = Energy Transferred$.</p> Signup and view all the answers

How can potential energy be defined in the context of magnetic energy?

<p>Potential energy in magnetic systems is the stored energy when magnets are positioned away from each other where attractions occur.</p> Signup and view all the answers

What is the importance of the variable 'g' in the weight equation?

<p>'g' represents the acceleration due to gravity, commonly taken as $10 ext{ N/kg}$ on Earth's surface.</p> Signup and view all the answers

Describe the relationship between force, mass, and acceleration using an equation.

<p>The relationship is defined by the equation $Force = Mass imes Acceleration$.</p> Signup and view all the answers

In which units is work measured, and how does it relate to energy?

<p>Work is measured in joules (J), and it is directly equivalent to energy in terms of units.</p> Signup and view all the answers

How is work done calculated in an engine?

<p>Work done is calculated using the formula $Work Done = Force \times Distance Moved$.</p> Signup and view all the answers

Define efficiency in the context of an engine.

<p>Efficiency is defined as the ratio of useful work done to total energy input, expressed as $Efficiency = {Useful Work Done \over Total Energy Input}$.</p> Signup and view all the answers

What does it mean if an engine has an efficiency of 25%?

<p>An efficiency of 25% means that the engine does 25 joules of useful work for every 100 joules of energy supplied.</p> Signup and view all the answers

Explain the relationship between the total energy output and total energy input in a system.

<p>The total energy output must equal the total energy input, reflecting the law of conservation of energy.</p> Signup and view all the answers

How do you calculate power, and what is its SI unit?

<p>Power is calculated using the formula $Power = {Work Done \over Time Taken}$, and its SI unit is the watt (W).</p> Signup and view all the answers

What historical significance does the horsepower (hp) unit have?

<p>Horsepower (hp) is a unit of power historically linked to steam engines and is equivalent to about 746 watts.</p> Signup and view all the answers

Provide an example of energy transfer in a power plant.

<p>In a power plant, energy transfers from fuel to electricity through stages like burning fuel to generate thermal energy, which drives turbines producing electricity.</p> Signup and view all the answers

Describe the energy transformation when a rubber band is released.

<p>When a rubber band is released, its elastic energy converts to kinetic energy, which becomes thermal energy upon impact with the ground.</p> Signup and view all the answers

Flashcards

Nuclear Energy

Energy stored within the nucleus of an atom and released when the nucleus splits or its particles rearrange.

Potential Energy

Energy stored in an object due to its position or configuration.

Thermal Energy

Energy associated with the random motion of particles within a substance.

Work Done

The amount of energy transferred when a force acts over a distance.

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Energy Transferred

The amount of energy that moves from one energy store to another.

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Mechanical Energy Transfer

Energy transferred using a force moving an object.

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Electrical Energy Transfer

Energy transferred by the flow of electric charge (current).

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Heat Transfer

Energy transferred due to temperature differences between objects.

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Efficiency

The ratio of useful work output to total energy input. It tells us how much of the input energy is converted into useful work.

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Power

The rate at which work is done or energy is transferred. It is calculated by dividing the work done by the time taken.

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Horsepower (hp)

A unit of power commonly used for engines. It is approximately equal to 746 watts.

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Law of Conservation of Energy

The total energy in a closed system remains constant. Energy cannot be created or destroyed, only transformed from one form to another.

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Kinetic Energy

The energy an object possesses due to its motion.

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Work (in physics)

Work is done when a force causes an object to move a certain distance in the direction of the force.

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Joule (J)

The SI unit of work and energy. One joule is the amount of work done when a force of one newton moves an object one meter in the direction of the force.

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Energy

The ability to do work. It's not a 'thing' itself, but a measure of how much work can be done.

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Gravitational Potential Energy

Energy stored by an object due to its position above the Earth's surface. The higher the object, the more potential energy it has.

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Elastic (Strain) Energy

Energy stored in a material that is stretched or compressed, like a rubber band or a spring.

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Chemical Energy

Energy stored in the bonds between atoms within molecules. This energy can be released through chemical reactions.

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Electrostatic Energy

Energy stored by electric charges that are held apart but attract each other.

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Study Notes

Work

  • Work is done when a force moves an object.
  • The greater the force and the distance moved, the more work is done.
  • The SI unit of work is the joule (J).
  • 1 joule of work is done when a force of 1 newton (N) moves an object 1 metre in the direction of the force.
  • Work is calculated using the equation: work done = force × distance moved in the direction of the force (W = Fd).

Energy

  • Energy is measured in joules (J).
  • Energy is stored in different ways.
  • Moving objects store kinetic energy.
  • Objects lifted upwards store gravitational potential energy.
  • Stretched objects (like rubber bands or springs) store elastic potential energy.
  • Chemical reactions store chemical energy.
  • Stored electric charges store electrostatic energy.
  • The particles inside atoms store nuclear energy.
  • Moving particles in materials store thermal energy.
  • Magnets store magnetic energy.
  • Energy can be transferred from one store to another.

Energy Stores

  • Kinetic energy is stored by moving objects.
  • Gravitational potential energy is stored by objects that are lifted against gravity.
  • Elastic potential energy is stored by stretching objects.
  • Chemical energy is stored in fuels, foods and batteries.
  • Electrostatic energy is stored in the electric charges that exist in objects.
  • Nuclear energy is stored in the nucleus of an atom.
  • Thermal energy is stored in the moving particles within materials.
  • Magnetic energy is stored by magnetic objects

Energy Pathways

  • Energy can be transferred mechanically (by a force moving something).
  • It can be transferred electrically (by an electric current).
  • It can be transferred through heating (because of a temperature difference).
  • It can be transferred by radiation (such as light waves and sound waves).

Conservation of Energy

  • Energy cannot be created or destroyed, only transferred from one store to another.
  • The total quantity of energy stays the same.

Work and Energy Transferred

  • Work done is equal to the energy transferred.
  • When work is done, energy is transferred from one store to another.
  • For an object of mass m at a vertical height h above the ground: gravitational potential energy = mgh.
  • For an object of mass m and speed v: kinetic energy = ½mv².

Efficiency

  • Efficiency is the percentage of energy that is usefully transferred.
  • Efficiency = (useful work done ÷ total energy input) ×100%

Power

  • Power is the rate at which work is done (or energy is transferred).
  • The SI unit of power is the watt (W).
  • Power = (work done ÷ time taken) or power = (energy transferred ÷ time taken).

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Work and Energy PDF

Description

Test your understanding of work and energy in physics. This quiz covers key concepts such as the definition of work, its SI unit, and different forms of energy storage. Brush up on your knowledge of kinetic and potential energy concepts to ace this quiz!

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