Chapter 9

Chapter 9

1. 9.1

   • Work is done when a net force acts on an object and the object moves in the direction of the net force.
   • Work is the product of the force on an object and the distance through which the object is m
   • W = Fd
   • The unit of work is the newton-meter (N•m), also called the joule

2. 9.2

   • Power equals the amount of work done divided by the time interval during which the work is done.
   • Power is the rate at which work is done
   • The unit of power is the joule per second, also known as the watt

3. 9.3

   • The two forms of mechanical energy are kinetic energy and potential energy.
   • The property of an object or system that enables it to do work is energy
   • mechanical energy is the energy due to the position of something or the movement of something
   • Energy due to motion is called kinetic energy, energy due to position or shape is called potential energy.

4. 9.4

   • Two examples of potential energy are elastic potential energy and gravitational potential energy.
   • Energy that is stored and held in readiness is called potential energy
   • gravitational potential energy = weight × height
   • PE = mgh
   • The amount of energy needed, or work that has to be done, to release potential energy is called activation energy

5. 9.5

   • The kinetic energy of a moving object is equal to the work required to bring it to its speed from rest, or the work the object can do while being brought to rest.
   • equal to half the mass multiplied by the square of the speed

6. 9.6

   • The work-energy theorem states that whenever work is done, energy changes.
   • The work-energy theorem describes the relationship between work and energy.
   • Work = ∆KE
   • The temperature of an object is related to the average speed of its molecules

7. 9.7

   • The law of conservation of energy states that energy cannot be created or destroyed. It can be transformed from one form into another, but the total amount of energy never changes.
   • The study of the forms of energy and the transformations from one form into another is the law of conservation of energy
   • Energy may change form, but the total energy stays the same.

8. 9.8

   • A machine transfers energy from one place to another or transforms it from one form to another; or redirects force, or magnifies force.
   • A machine is a device used to multiply forces or simply to change the direction of forces.
   • Mech. Advantage= d/d=L/L=F/F

9. 9.9

   • The mechanical advantage of a ramp is the length divided by the height.
   • L/h=F/F
   • A machine cannot put out more energy than is put into it… and usually it puts out LESS energy that was put into it.
   • In any machine, some energy is transformed into atomic or molecular kinetic energy—making the machine warmer. No machine is 100% efficient in converting energy to another form or place.

10. 9.11

    • Almost every aspect of our way of life depends on the availability of large amounts of energy.
    • Oil, natural gas, and coal are all examples of fossil fuels.
    • Sunlight can also be used to heat water, which is stored in an insulated container
    • As water flows from the reservoir to the outflow, its gravitational potential energy becomes kinetic energy, and used to spin turbine blades to drive electrical generators.
    • Each uranium fission produces neutrons that can cause additional fission reactions
    • The most concentrated form of usable energy is stored in uranium and plutonium, which are nuclear fuels.

11. Sanjana Dixit

    • Feb. 9 2015