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chapt 7

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Terms in this set (22)

  • What does the Work-Energy Theorem state?
    Any change in kinetic energy is the result of work done on the object, expressed as \(W=\Delta KE\).
  • How does work relate to an object's speed when starting from rest?
    If an object obtains twice the speed, it has been subject to four times the work.
  • What is the formula for work done by a force?
    Work is the product of force and distance moved in the direction of the force: \(W=Fd\).
  • What is the unit of work and its equivalent in base units?
    The unit of work is the joule (J), where 1 J = 1 newton × 1 meter (1 N·m).
  • What is the law of conservation of energy?
    Energy cannot be created or destroyed; it can only be transformed from one form to another, with the total energy remaining constant.
  • What are the two main forms of mechanical energy?
    Mechanical energy consists of potential energy (due to position) and kinetic energy (due to motion).
  • How is gravitational potential energy calculated?
    Potential energy is given by \(PE=mgh\), where m is mass, g is gravitational acceleration, and h is height.
  • What is kinetic energy and its formula?
    Kinetic energy is the energy of motion, calculated as \(KE=\frac{1}{2}mv^2\).
  • How does kinetic energy change if speed doubles?
    If speed doubles, kinetic energy increases by a factor of four.
  • What is the difference between momentum and kinetic energy?
    Momentum is a vector quantity depending linearly on velocity, while kinetic energy is a scalar quantity depending on the square of velocity.
  • What is power in physics?
    Power is the rate at which work is done, calculated as work done divided by time interval.
  • What is the unit of power and its relation to work and time?
    Power is measured in watts (W), where 1 W = 1 joule per second (1 J/s).
  • What is the principle of a machine regarding work input and output?
    An ideal machine conserves energy, so work input equals work output: \(F_{in}d_{in} = F_{out}d_{out}\).
  • What does a lever do as a simple machine?
    A lever rotates on a fulcrum and allows a small force over a large distance to produce a large force over a short distance.
  • How does a pulley system affect force and distance?
    A pulley changes the direction of the input force and can multiply force when arranged as a block and tackle.
  • How is efficiency of a machine defined?
    Efficiency is the percentage of work input converted into useful work output, calculated as useful energy output divided by total energy input.
  • What does it mean if a machine is 30% efficient?
    It converts 30% of the energy input into useful work, with 70% lost as waste energy.
  • What is recycled energy?
    Recycled energy is the reuse of energy that would otherwise be wasted, such as using heat from power plants to warm buildings.
  • How does the human body obtain energy?
    The body uses energy stored in food hydrocarbons, which release energy when reacting with oxygen.
  • What are some renewable sources of energy from the Sun?
    Sunlight evaporates water for hydroelectric power, photovoltaic cells convert sunlight to electricity, and wind power drives turbines.
  • How does a fuel cell produce electricity?
    Hydrogen and oxygen are compressed at electrodes, producing electric current and water as a byproduct.
  • What is geothermal energy and how is it used?
    Geothermal energy is heat stored underground, used to produce steam that drives turbines for electricity generation.