work power energy Flashcards
work done is?
integration from A to B of F.ds
what does this ds depend on
it does not depend on force applied. it may or may not be caused by the force
what is the exact definition of work done
force*(displacement caused at the point of application)
if body moves in a curvillinear path and F is constant
W=F.s
work done in circular motion
0
work done by gravity is
mgh from moving up to down
-mgh from moving down to up
work_total=
integration of f_net.ds
total work done by all forces is
work done by net force
work done by variable force is
integration of (fxi+fyj+fzk).(dxi+dyj+dzk)
if force acts in only x direction
displacement is only in x axis and W=integration(Fxdx)
if F=f(x)
W=integration of f(x)dx from x1 to x2
work done by spring force
1/2kx1^2-1/2kx2^2
what are the limits of integration in compression
from 0 to -x
work done in a different frame of reference
integration of F.ds(in the frame of reference)
total work done by all forces
total change in kinetic energy
if 2 different springs (not attached to each other) is acting on a body
k_equivalent=k1+k2
if 2 different springs (attached to each other) is acting on a body
1/k_eq=1/k1+1/k2
what is the work done by a system of bodies
total change in kinetic energy of system of bodies
what is a conservative force
work done is independent of path and only depends on initial and final points
what is a non-conservative force
work done is dependent of path
what is potential energy
energy possessed by virtue of position
when does potential energy change
only when conservative force does work
formula of potential energy
-(work done by conservative force)
where is the potential energy 0
the potential energy is 0 at the reference point
whAT IS principle of conservation of mechanical energy
Uf+KEf=Ui+KEi
what is mechanical energy
U+KE
what is work done by non conservative and external forces
change in mechanical energy
how to find fx fy and fz
partially differentiate U wrt dx dy and dz respectively
eg if U=3x^2yz find fx,fy and fz
fx=6xyz
fy=3x^2z
fz=3x^2y
whats stable equilibrium
its a position where the body shows tendency to the equilibrium upon being disturbed from equilibrium
whats unstable equilibrium
equilibrium position where the body shows tendency to move away from equilibrium upon being disturbed
whats neutral equilibrium
equilibrium which is neither stable nor unstable
at stABLE EQUILIBRIUM
PE IS MINIMUM
at unstable equilibrium
PE is maximum
how do you get to know if a body is in stable or unstable equlilbrium
dU/dx=0
how to represent stable unstable and neutral equilibrium on graph
local minimum is stable equilibrium
local maxima is unstable equiibrium
a straight line represents neutral equilibrium
what is power
rate of doing work
average power
work done/time interval
instantaneous power
dW/dt
F.v
total of average powers due to all forces on a body
change in ke by time
total of instantaneous powers due to all forces on a body
d(ke)/dt
