chapter 9 test Flashcards
what is conserved?
mechanical energy is conserved when there is no net work done by external forces
Kinetic energy equation
KE= 1/2 mv^2
Gravitational Potential Energy equation
PE = mgh
Spring potential energy equation
PE = 1/2 kx^2
What does the term mechanical energy refer to?
the sum of a systems kinetic and potential energy
positive work is…
is done by a force PARALLEL to an objects displacement
negative work is …
is done by a force ANTIPARALLEL to an objects displacement
when a force is acting perpendicular to an object displacement …
no work is done
what type of quantity is work?
scalar because it can be positive or negative but it does not have a direction
in a force vs. displacement graph what is the work?
the area underneath the graph
power
the amount of work done in one second, or energy used in one second
power equation
P = w/t
unit for power
watts
unit for work
joules
what does the mechanical advantage of a simple machine tell you?
how much the input force is multipled to give you the output force
whats the MA of a pulley?
the number of supporting tensions
in an ideal simple machine the …
work in equals the work out
the efficiency tells you…
how much energy is lost in any process for a simple machine
what is the percent of efficiency in an ideal simple machine?
100%
energy
the ability to do work
potential energy
the energy of a position/shape/ or configuration
elastic potential energy
potential energy that is stored in a spring or other elastic material
what are examples of simple machines?
lever, pulley, wedge, inclined plane, wheel, axel, screw
what does a simple machine do?
augments or multiples an applied force
pulley
a simple machine that can change the direction and multiply an applied force
efficiency equation
e = work out/ work in x 100%
in most real-life simple machines…
some input work is lost due to friction so the work in does NOT equal the work out , and the efficiency is less than 100%
