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.</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</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</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.</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.</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</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</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.</p> Signup and view all the answers

    Which factor is NOT considered when calculating work done?

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

    What is Newton’s Second Law commonly expressed as?

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

    How can kinetic energy be transformed within a system?

    <p>Into sound energy as the object moves</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.</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$</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.</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.</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</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$</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.</p> Signup and view all the answers

    How is power defined in the context of energy transfer?

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

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

    <p>P = ΔW / Δt</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</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</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</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</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</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.</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</p> Signup and view all the answers

    What does the principle of conservation of energy state?

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

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

    <p>Elastic potential energy</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.</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</p> Signup and view all the answers

    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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