Physics Chapter 3: Work and Machines Flashcards
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Questions and Answers

What is the formula for work?

  • Force x Distance (correct)
  • Distance / Time
  • Force + Distance
  • Force / Distance

    • What is power?

    The rate at which work is done.

    What is the SI unit of energy?

    Joule

    What is a watt?

    <p>A measure of power equal to one joule of work per second.</p> Signup and view all the answers

    Work divided by time equals what?

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

    What is the unit of work?

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

    What is the unit of power?

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

    Force multiplied by distance equals what?

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

    Work is done on an object when the object moves in the same direction in which the force is applied.

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

    If you pull at an angle instead of in the direction in which the object moves, more of your force does work.

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

    The farther you move an object, the more work you do.

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

    The more power you use to move an object, the more work you do.

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

    Power is the rate at which work is done.

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

    What is a machine?

    <p>A device that makes work easier.</p> Signup and view all the answers

    What is input force?

    <p>The force exerted on a machine.</p> Signup and view all the answers

    What is output force?

    <p>The force exerted on an object by a machine.</p> Signup and view all the answers

    What is mechanical advantage?

    <p>The number of times a machine increases a force exerted on it.</p> Signup and view all the answers

    What is efficiency?

    <p>The percentage of the input work that is converted to output work.</p> Signup and view all the answers

    Machines are devices that allow you to _______________________ in an easier way.

    <p>do work</p> Signup and view all the answers

    The force you exert when you use a machine is the _________________

    <p>input force</p> Signup and view all the answers

    The force exerted by the machine is the _________________

    <p>output force</p> Signup and view all the answers

    The force you exert on an object multiplied by the distance the object moves is equal to __________________, which is expressed in joules.

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

    Divide output work by input work and multiply by 100% to find a machine's ______________

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

    A machine's mechanical advantage is the output force multiplied by the input force.

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

    If the output force is greater than the input force, the mechanical advantage of the machine is greater than one.

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

    If the machine increases distance, the output force is greater than the input force.

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

    If a machine changes the direction but not the amount of the input force, the mechanical advantage is greater than 1.

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

    An ideal machine has no friction.

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

    What is an inclined plane?

    <p>A flat, sloped surface.</p> Signup and view all the answers

    What is a wedge?

    <p>A device that is thick at one end and tapers to a thin edge at the other end.</p> Signup and view all the answers

    What is a screw?

    <p>An inclined plane wrapped around a cylinder.</p> Signup and view all the answers

    What is a lever?

    <p>A rigid bar that is free to move around a fixed point.</p> Signup and view all the answers

    What is a fulcrum?

    <p>The fixed point around which a lever pivots.</p> Signup and view all the answers

    The ideal mechanical advantage of an inclined plane is the length of the plane divided by its force.

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

    When you use a wedge, instead of moving an object along the inclined plane, you move the inclined plane itself.

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

    The thicker the wedge, the greater its mechanical advantage.

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

    In a first-class lever, the fulcrum is between the input force and the output force.

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

    A knife is an example of a lever.

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

    The lower arm acts like a first-class lever when it bends at the elbow.

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

    A flat sloped surface is called a(n) ____________________.

    <p>inclined plane</p> Signup and view all the answers

    A device that is thick at one end and thin at the other end is a ____________________.

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

    The threads of a screw act like a(n) ____________________.

    <p>inclined plane</p> Signup and view all the answers

    The fixed point that a lever pivots around is the ____________________.

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

    What is a pulley?

    <p>A simple machine that consists of a rope that fits into a groove in a wheel.</p> Signup and view all the answers

    What is a wheel and axle?

    <p>Two different sized circular objects that are attached together and turn as one.</p> Signup and view all the answers

    What is a compound machine?

    <p>A machine made of more than one simple machine.</p> Signup and view all the answers

    One of the simple machines that turns is the wheel and ______________.

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

    A single fixed pulley changes the ____________________ of a force.

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

    A system of fixed and _______________________ pulleys is called a block and tackle.

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

    A screwdriver and a doorknob are examples of a(n) ______________________.

    <p>wheel and axle</p> Signup and view all the answers

    In a compound machine, the ___________________ of one simple machine becomes the input force of another simple machine.

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

    If a compound machine is made of a pulley with a mechanical advantage of 3 and a wheel and axle with a mechanical advantage of 5, the mechanical advantage of the compound machine is 8.

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

    To find the mechanical advantage of a wheel and axle, multiply the radius of the wheel by the radius of the axle.

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

    To find the mechanical advantage of a pulley, count the sections of rope that support the object.

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

    A bicycle is a compound machine because it contains more than one simple machine.

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

    The part of a wheel and axle with the smaller radius is the wheel.

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

    For work to be done on an object, ____________________.

    <p>the object must move some distance as a result of a force</p> Signup and view all the answers

    If you exert a force of 20 newtons to push a desk 10 meters, how much work do you do on the desk?

    <p>200 joules</p> Signup and view all the answers

    The mechanical advantage of a machine is the number of times a machine increases ____________________.

    <p>the amount of friction</p> Signup and view all the answers

    What is a simple machine that might be thought of as an inclined plane that moves?

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

    Give an example of a compound machine.

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

    What is the ideal mechanical advantage for an inclined plane?

    <p>Equal to the length of the incline divided by the height of the incline.</p> Signup and view all the answers

    How can a hockey stick be considered a machine?

    <p>It multiplies distance.</p> Signup and view all the answers

    If tight scissors have an efficiency of 50 percent, what does that mean?

    <p>Half of your work is wasted due to input force.</p> Signup and view all the answers

    Power is measured in units called?

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

    The wedge, screw, and lever are all?

    <p>Simple machines</p> Signup and view all the answers

    What is a screwdriver?

    <p>A simple machine called a wheel and axle.</p> Signup and view all the answers

    A device that is twice as powerful as another can do ___________________ the amount of work in the same amount of time.

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

    A machine makes work easier by multiplying force or __________________, or by changing direction.

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

    A ramp in a parking garage is an example of a simple machine called a(n)?

    <p>Inclined plane</p> Signup and view all the answers

    Power is equal to ______ divided by time.

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

    The force exerted by a machine is called the output force.

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

    A wheel and axle is a compound machine.

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

    The ideal mechanical advantage of a wheel and axle is the radius of the wheel times the radius of the axle.

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

    You do work on an object when you lift it off the floor onto a shelf.

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

    Joule is the rate at which work is done.

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

    Is machine 1 classified as a simple or a compound machine?

    <p>It is classified as a simple machine because the only simple machine that is there is a pulley.</p> Signup and view all the answers

    In machine 2, which letter represents the input force?

    <p>The letter that represents the input force is G.</p> Signup and view all the answers

    Which machines multiply the input force?

    <p>Letter F</p> Signup and view all the answers

    A bricklayer lifts a stack of bricks onto his shoulder, carries it across a room, and then lifts the bricks onto a ledge above his head. Explain if work is being done in each of these three situations.

    <p>Yes because he is using a ledge which is a simple machine.</p> Signup and view all the answers

    Explain how the ideal mechanical advantage and efficiency of a machine determine the machine's actual mechanical advantage.

    <p>100 because it is the ideal mechanical advantage so it determinants the actual M.A from 100.</p> Signup and view all the answers

    In what class of lever is the direction of the input force opposite to the direction of the output force?

    <p>The first class levers</p> Signup and view all the answers

    To which class of lever does each of the following machines belong: (i) fishing pole; (ii) wheelbarrow; (iii) bottle opener; (iv) pliers?

    <p>A fishing pole is a third class lever, A wheelbarrow is a second class lever. A bottle opener is a second class lever. Pliers is second class.</p> Signup and view all the answers

    Explain why wedges and screws are actually types of inclined planes.

    <p>A wedge is a triangular shaped object, and is a portable inclined plane. It's one of six simple machines.</p> Signup and view all the answers

    The output force of a lever with an ideal mechanical advantage of 3 is used as the input force of a pulley system with an ideal mechanical advantage of 2. What is the ideal mechanical advantage of the compound machine? Explain.

    <p>It would be 6 because 3 times 2 equals 6.</p> Signup and view all the answers

    Why is it more difficult to steer a bike when your hands are close together on the handlebars than when they are far apart?

    <p>It's harder to steer a bike when your hands are close together on the handlebar than when they are farther apart because that is just how things work.</p> Signup and view all the answers

    Study Notes

    Work and Energy

    • Work is defined as force multiplied by distance; its unit of measurement is the joule (J).
    • Power is the rate at which work is done and is measured in watts (W), where 1 watt equals 1 joule per second.
    • The efficiency of a machine indicates the percentage of input work converted to output work.

    Machines

    • A machine is a device that makes work easier by increasing force, distance, or changing the direction of force.
    • The force applied to a machine is called input force, while the force exerted by the machine is the output force.
    • Mechanical advantage is the factor by which a machine increases the input force, calculated as output force divided by input force.

    Types of Simple Machines

    • Simple machines perform work with a single movement and include:
      • Inclined Plane: A flat sloped surface that allows lifting objects more easily.
      • Wedge: A device that tapers to a thin edge, facilitating splitting or lifting.
      • Screw: An inclined plane wrapped around a cylinder.
      • Lever: A rigid bar that moves around a fixed point known as the fulcrum.
      • Pulley: A wheel with a groove that changes the direction of a force.
      • Wheel and Axle: Comprises two circular objects that rotate together, aiding in movement.

    Mechanical Advantage and Efficiency

    • The ideal mechanical advantage for an inclined plane is its length divided by the height of the incline.
    • In a compound machine, the output of one machine acts as the input for another, affecting overall efficiency.
    • The effectiveness of a machine can be impacted by factors like friction, with an ideal machine having no friction.

    Working with Forces

    • Work is only done when an object moves in the same direction as the applied force, and this factor is crucial in calculating the work done on an object.
    • If multiple forces are applied, only the component of the force in the direction of motion does work.

    True or False Statements

    • Work is done lifting an object if it moves; lifting is not the only condition to consider work done.
    • The rate of doing work (power) does not equate to doing more work but rather doing work faster.

    Class of Levers

    • The configuration of forces in levers and their classes affect their functioning:
      • First Class Lever: Fulcrum is between input and output forces (e.g., seesaw).
      • Second Class Lever: Output force is between input force and fulcrum (e.g., wheelbarrow).
      • Third Class Lever: Input force is between output force and fulcrum (e.g., fishing pole).

    Practical Examples

    • A bicycle is classified as a compound machine due to its multiple simple machines.
    • A common application of a screw is its thread, acting as an inclined plane to convert rotational force to linear motion.

    Working and Tools

    • Household tools like screwdrivers are simple machines designed to ease tasks by amplifying applied forces or altering motion direction.
    • Understanding the mechanics behind these machines allows for more efficient use in practical applications.

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    Test your understanding of key concepts related to work and machines with these flashcards. Each card defines essential terms such as work, power, and the units of energy. Perfect for reviewing before your exam!

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