Chapter 4: Work and Energy Flashcards
force applied through a distance; measure of energy transfer that occurs when an object is moved over a distance by an external force
work
a device that changes the force or increases the motion from work
machine
a machine that does work with only one movement of the machine
simple machine
six types of simple machines:
lever, pulley, wheel and axle, inclined plane, screw, and wedge
a combination of two or more simple machines
compound machine
the ratio of output work to input work
efficiency
the ratio of the output force to input force
mechanical advantage
the ability to cause change
energy
energy that is due to chemical bonds
chemical potential energy
energy that is stored by compressing or stretching an object
elastic potential energy
energy due to motion
kinetic energy
energy that is stored due to the interactions between objects
potential energy
anything around which you can imagine a boundary; can be a single object or a group of objects
system
energy that is due to the gravitational forces between objects
gravitational potential energy
states that energy cannot be created or destroyed; energy can only be converted from one form to another or transferred from one place to another
law of conservation of energy
the sum of the kinetic energy and potential energy of the objects in a system
mechanical energy
the rate at which energy is converted
power
the equation for work is:
work (J) = applied force (N) * distance (m)
W = Fd
the equation to find efficiency is:
efficiency (%) = output work (J) /input work (J) * 100
e = Wout/Win* 100
what is the equation to find mechanical advantage
mechanical advantage = output force (N) / input force (N)
MA = Fout/Fin
the equation to find kinetic energy:
kinetic energy (J) = 1/2 mass (kg) * [speed (in m/s)]^2
KE = 1/2mv^2
the equation to find gravitational potential energy:
gravitational potential energy (J) = mass (kg) * gravity (N/kg) * height (m)
GPE = mgh
power equation:
Power (watts) = Energy (J) / time (s)
P = E/t
Machines make doing work ______ or ________ by ______________________.
easier; faster; changing the force needed to do the work
3 possible functions of a machine:
increase speed, change direction of a force, or increase force
relative to the input work on a machine, the output work from that machine is…
never as great
forms of energy
mechanical, electrical, chemical, thermal, radiant
different forms of potential energy:
elastic, chemical, and gravitational
energy cannot be created or destroyed. what can it do/what can happen to it?
energy can be transferred between forms
mechanical energy is the sum of…
all of the potential energies and kinetic energies of all the objects in a system
