Work, Energy, and Power Concepts
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Questions and Answers

What is the formula for gravitational potential energy change near the Earth's surface?

  • ΔE p = mgΔh (correct)
  • ΔE p = mg/s
  • ΔE p = mgh
  • ΔE p = 0.5mv^2

What does the elasticity/spring constant affect in the context of potential energy?

  • Kinetic energy
  • Thermal energy
  • Elastic potential energy (correct)
  • Gravitational potential energy

How is kinetic energy (E k) derived in relation to mass and speed?

  • E k = ma^2
  • E k = 2ma
  • E k = 0.5mv^2 (correct)
  • E k = mv^2s

Which of the following reflects a decrease in gravitational potential energy?

<p>An object is dropped from a higher position. (A)</p> Signup and view all the answers

What causes the difference between the initial kinetic energy and the maximum gravitational potential energy of a ball that has stopped in mid-air?

<p>Energy transferred to the environment as heat due to air resistance (D)</p> Signup and view all the answers

How is work done on a gas calculated when it is at constant pressure?

<p>Work done = pΔV (C)</p> Signup and view all the answers

What is the relationship between force, distance, and work done?

<p>Work done is the product of force and distance travelled. (D)</p> Signup and view all the answers

Which statement is true regarding mass and elastic potential energy?

<p>Elastic potential energy depends on mass and spring constant. (B)</p> Signup and view all the answers

Which of the following formulas represents efficiency as a percentage?

<p>Efficiency = (useful output power / input power) × 100 (B)</p> Signup and view all the answers

What is the formula for calculating kinetic energy of an object?

<p>E_k = 1/2 mv^2 (C)</p> Signup and view all the answers

What happens to an object's gravitational potential energy when it does positive work?

<p>Its gravitational potential energy increases. (B)</p> Signup and view all the answers

Which factor is NOT considered when calculating work done?

<p>Mass of the object (A)</p> Signup and view all the answers

What is Newton’s Second Law commonly expressed as?

<p>F = ma (B)</p> Signup and view all the answers

Why is the efficiency of a system never considered to be 100%?

<p>Energy is lost due to friction and other forms of energy transfer (B)</p> Signup and view all the answers

What does θ represent in the work done formula W = F s cos θ?

<p>The angle between the force and the distance travelled (A)</p> Signup and view all the answers

How can kinetic energy be transformed within a system?

<p>Into sound energy as the object moves (B)</p> Signup and view all the answers

If an object is lifted vertically with a constant velocity, what must be true about the forces acting on it?

<p>The applied force is equal to the weight of the object. (B)</p> Signup and view all the answers

What equation represents the relationship between work done and change in potential energy?

<p>$ ext{Work done} = mgΔh$ (C)</p> Signup and view all the answers

In the context of a simple pendulum, what is the potential energy at the maximum height of the swing?

<p>It is at its maximum value at that point. (C)</p> Signup and view all the answers

When calculating the maximum speed of a pendulum, which principle is primarily used?

<p>Principle of conservation of energy. (B)</p> Signup and view all the answers

What is the correct calculation for the gravitational potential energy of a mass of 500g raised by a height of 10cm?

<p>0.4905 J (D)</p> Signup and view all the answers

What formula is used to derive the maximum speed of the pendulum from its potential energy?

<p>$ rac{1}{2} mv^2 = mgh$ (B)</p> Signup and view all the answers

Why can air resistance be ignored in calculations involving the pendulum’s motion?

<p>It does not affect the total energy. (A)</p> Signup and view all the answers

How is power defined in the context of energy transfer?

<p>Energy transferred divided by time. (B)</p> Signup and view all the answers

What is the formula used to calculate power based on work and time?

<p>P = ΔW / Δt (C)</p> Signup and view all the answers

To calculate the energy transferred by an electrical appliance, what product should be used?

<p>Power and time (A)</p> Signup and view all the answers

If a kettle requires 163800 J of energy and has a power rating of 1200 W, how long will it take to boil 0.5 kg of water?

<p>136.5 seconds (D)</p> Signup and view all the answers

What is the kinetic energy gained by a 0.6 kg ball that accelerates to 12 m/s?

<p>43.2 J (D)</p> Signup and view all the answers

What force is generated by a car traveling at a constant velocity of 15 m/s against a frictional force of 200 N?

<p>200 N (B)</p> Signup and view all the answers

How is power calculated for a car traveling at constant velocity against a frictional force?

<p>P = F × v (B)</p> Signup and view all the answers

Which of the following is true about energy transfer in the context of electrical appliances?

<p>It is equal to the product of power and time. (B)</p> Signup and view all the answers

If the average power gained by an accelerating ball is 216 W, how much energy was transferred if the time taken was 0.2 s?

<p>43.2 J (C)</p> Signup and view all the answers

What does the principle of conservation of energy state?

<p>Energy can neither be created nor destroyed. (D)</p> Signup and view all the answers

Which type of energy is dependent on an object's height above the ground?

<p>Gravitational potential energy (D)</p> Signup and view all the answers

How is energy transferred when a spring is compressed?

<p>Kinetic energy is converted into elastic potential energy. (A)</p> Signup and view all the answers

What happens to the kinetic energy of a ball thrown upwards as it rises?

<p>It decreases as it converts to gravitational potential energy. (D)</p> Signup and view all the answers

Which statement correctly describes internal energy?

<p>It is the sum of all kinetic and potential energies of an object's particles. (C)</p> Signup and view all the answers

When an object is squashed, what form of energy is primarily stored?

<p>Elastic potential energy (D)</p> Signup and view all the answers

What result occurs when a ball reaches its highest point after being thrown?

<p>All kinetic energy has converted into gravitational potential energy. (B)</p> Signup and view all the answers

When thermal/internal energy is emitted by a radiator, through which form is it transmitted?

<p>Infrared radiation (D)</p> Signup and view all the answers

Flashcards

Conservation of Energy

The total energy of a closed system remains constant.

Energy

The ability to do work.

Gravitational Potential Energy

Energy stored due to an object's position within a gravitational field.

Kinetic Energy

Energy stored by a moving object.

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Internal Energy

The sum of all kinetic and potential energies of all particles within an object.

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Elastic Potential Energy

Energy stored in an elastic object that has been deformed (stretched or compressed).

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Electrical Potential Energy

Energy stored by a charged object within an electric field.

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Energy Conversion

The process of transferring energy from one form to another.

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Work Done

The work done by a force causing motion is the product of the force and the distance moved in the direction of the force.

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Kinetic Energy (Ek)

The energy an object possesses due to its motion.

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Potential Energy (Ep)

The energy an object possesses due to its position or state.

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Work

The amount of energy transferred or transformed when a force causes an object to move a certain distance.

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Efficiency

The ratio of useful power output to total power input.

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Efficiency (Percentage)

The measure of how well a system converts energy into useful work.

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Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed from one form to another.

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Work-Energy Theorem

The work-energy theorem states that the net work done on an object is equal to the change in its kinetic energy.

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Energy Conservation

The process of converting one form of energy into another, without any loss or gain of energy. We can convert kinetic energy into potential energy, and vice versa.

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Change in Gravitational Potential Energy

The change in an object's gravitational potential energy is equal to its mass multiplied by the acceleration due to gravity and the change in its height.

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Earth's Gravitational Field

A uniform force that pulls on all objects towards the center of the Earth.

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Power

The amount of energy transferred per unit time.

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Work-energy theorem (Gravitational Potential Energy)

The work done on an object is equal to the change in its gravitational potential energy. This change is independent of the path taken; only the initial and final heights matter.

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Work done against gravity

The work done against gravity to lift an object to a certain height is stored as gravitational potential energy.

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Pendulum Speed & Energy

The maximum speed a simple pendulum reaches during its swing is determined by the potential energy at its highest point, which is converted into kinetic energy at its lowest point.

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Air Resistance

Air resistance is a force that opposes motion through the air, reducing the energy of a system. In calculations, we sometimes ignore its effects to simplify the problem.

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Power = Force x Velocity

The formula for calculating power, which is the product of force and velocity.

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Work Done by an Electrical Appliance

The work done by an electrical appliance is equal to the product of its power and the time it operates.

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Power as Energy Transfer Rate

The energy transferred per unit time.

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Energy Transferred

The product of power and time passed.

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Study Notes

Work, Energy, and Power

  • Energy Conservation: Energy cannot be created or destroyed, only transferred between forms. The total energy in a closed system stays constant.

  • Energy Forms: Energy exists in various forms, including:

    • Gravitational potential energy (dependent on height and mass)
    • Kinetic energy (dependent on mass and velocity)
    • Internal energy (sum of kinetic and potential energies of particles)
    • Elastic potential energy (stored in stretched or compressed objects)
    • Electrical potential energy (dependent on a charge's position in an electric field)

  • Energy Transfer: Energy transfers occur when:

    • Work is done (e.g., squashing an object converts kinetic to elastic potential energy)
    • Energy is absorbed or emitted as electromagnetic radiation (e.g., infrared radiation)

  • Example - Ball Toss: When a ball is thrown upwards, kinetic energy is initially high, converting to gravitational potential energy as it rises, and back to kinetic energy as it falls.

Work

  • Definition: Work (W) is the force causing motion multiplied by the distance traveled in the direction of the motion.

  • Formula: W = Fs cos θ, where:

    • F is the force
    • s is the distance traveled
    • θ is the angle between the force and the direction of motion

Efficiency

  • Definition: Efficiency measures how effectively a system transfers energy. It is the ratio of the useful output power to the total input power.

  • Formula: Efficiency = (useful output power / input power) x 100%

  • Limit: Efficiency is always less than 100% because some energy is always lost (e.g., to friction).

Kinetic Energy

  • Definition: Kinetic energy (Ek) is the energy an object possesses due to its motion.

  • Formula: Ek = 1/2mv², where:

    • m is the mass of the object
    • v is the velocity of the object

Potential Energy (Gravitational)

  • Definition: Gravitational potential energy (Ep) is the energy an object possesses due to its position in a gravitational field.

  • Formula (near Earth's surface): ΔEp = mgΔh, where:

    • m is the mass of the object
    • g is the acceleration due to gravity
    • Δh is the change in height

Power

  • Definition: Power (P) is the rate of energy transfer (or work done).

  • Formula: P = W/t (where W is work done and t is time)

    • Alternatively: P = Fv (where F is force and v is velocity)

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CAIE Physics A-level Notes - Work, Energy, and Power PDF

Description

Explore the foundational principles of work, energy, and power in this quiz. Understand energy conservation, different forms of energy, and how energy transfers occur. Test your knowledge with examples such as the energy dynamics of a tossed ball.

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