Physics Work and Energy Concepts
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Questions and Answers

What defines work done by a force on an object?

  • A force must be exerted without any movement.
  • The object must rotate as a result of the force.
  • The object must move due to the force exerted. (correct)
  • The force must exceed the weight of the object.

    • What is the SI unit of work?

  • Newton
  • Meter
  • Joule (correct)
  • Pound

    • Which of the following describes positive work?

  • When force and displacement are in opposite directions.
  • When force has no component in the direction of displacement.
  • When the force is applied perpendicular to the displacement.
  • When force has a component in the direction of displacement. (correct)

    • What is the relationship between work and kinetic energy?

    <p>Total work done changes an object's kinetic energy.</p> Signup and view all the answers

    What happens to the work done if the force is exerted at an angle to the displacement?

    <p>Work can still be calculated using components of force.</p> Signup and view all the answers

    Which of these statements is true regarding the work done against gravity?

    <p>It is equal to the weight of the object times the height lifted.</p> Signup and view all the answers

    Which of the following equations represents work done by a constant force?

    <p>W = F × d</p> Signup and view all the answers

    What characterizes negative work?

    <p>The force has a component opposite to the direction of displacement.</p> Signup and view all the answers

    What is true when the force is perpendicular to the displacement of an object?

    <p>The force does no work.</p> Signup and view all the answers

    What happens to the kinetic energy of a particle when it is at rest?

    <p>It is always zero.</p> Signup and view all the answers

    How does kinetic energy change with the speed of an object?

    <p>It increases with the square of speed.</p> Signup and view all the answers

    According to the work-energy theorem, what does the work done by the net force on a particle equal?

    <p>The change in kinetic energy.</p> Signup and view all the answers

    What is true about the work done by external forces acting on the skater?

    <p>It does not change the kinetic energy.</p> Signup and view all the answers

    What effect does total work have on a particle's speed?

    <p>It speeds up if total work is positive.</p> Signup and view all the answers

    What is the relationship between mass and kinetic energy?

    <p>Kinetic energy increases linearly with mass.</p> Signup and view all the answers

    When does a weightlifter do no work on a barbell?

    <p>When he holds it stationary.</p> Signup and view all the answers

    What does the work done by a varying force from position $x_1$ to $x_2$ depend on?

    <p>The area under the force versus position curve</p> Signup and view all the answers

    How is the work done on a spring to stretch it a distance $X$ expressed mathematically?

    <p>$W = rac{1}{2}kX^2$</p> Signup and view all the answers

    What is the SI unit of power?

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

    Which of the following formulas represents average power?

    <p>$P_{avg} = \frac{W}{t}$</p> Signup and view all the answers

    What is the relationship between force and the distance a spring is stretched?

    <p>Force is directly proportional to distance</p> Signup and view all the answers

    In the context of motion along a curve, how is work found?

    <p>Through a line integral of the force vector</p> Signup and view all the answers

    What is instantaneous power?

    <p>The power calculated at a specific moment</p> Signup and view all the answers

    If a force varies with position, what is the first step to calculate the total work done?

    <p>Divide the displacement into smaller segments</p> Signup and view all the answers

    Study Notes

    Work

    • Work done by a force involves a displacement of the object the force is acting on.
    • Unit of work is the Joule (J) which is defined as 1 Newton (N) of force multiplied by 1 meter (m) of distance.
    • Positive work occurs when the force component is in the direction of displacement.
    • Negative work occurs when the force component acts opposite to the direction of displacement.
    • Zero work occurs when the force is perpendicular to the displacement.

    Kinetic Energy

    • The energy of motion of an object is referred to as kinetic energy.
    • The amount of kinetic energy is dependent on mass and speed, not direction.
    • Kinetic energy can never be negative and is only zero when the object is at rest.
    • The SI unit of kinetic energy is the Joule.

    Work-Energy Theorem

    • The work done by the net force on a particle is equal to the change in the particle's kinetic energy.

    Power

    • Power is the rate at which work is done.
    • Average power is calculated by dividing the work done by the time taken.
    • Instantaneous power is calculated by taking the derivative of work with respect to time.
    • The SI unit of power is the Watt (W), which is equivalent to 1 Joule (J) per second (s).
    • Another unit of power is the horsepower (hp) which is equivalent to 746 Watts (W).

    Work Done by a Varying Force

    • When the force is not constant, the work done can be calculated by integrating the force over the displacement.
    • The total work done by the force over a distance is represented by the area under the curve of force versus position.

    Work - Energy Theorem for Curved Path

    • The work done by a force along a curved path is represented by a line integral of the force along the path.

    Stretching a Spring

    • The force required to stretch a spring is proportional to the distance it is stretched.
    • The work done to stretch a spring is equal to 1/2 times the spring constant (k) multiplied by the square of the distance stretched.

    Examples

    • When a force is applied to an object at an angle to the direction of motion, only the component of the force parallel to the motion will do work.
    • The work-energy theorem can be used to calculate the speed of an object after a certain amount of work has been done on it.
    • The power output of a motor can be calculated by dividing the work done by the time taken.

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    University Physics With Modern Physics Chapter 6 PDF

    Description

    Dive into the fascinating concepts of work, kinetic energy, and power in physics. This quiz covers the essentials of how work is defined, the work-energy theorem, and the relationship between force and energy. Test your understanding of these fundamental principles!

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