work power energy Flashcards

1
Q

work done is?

A

integration from A to B of F.ds

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2
Q

what does this ds depend on

A

it does not depend on force applied. it may or may not be caused by the force

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3
Q

what is the exact definition of work done

A

force*(displacement caused at the point of application)

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4
Q

if body moves in a curvillinear path and F is constant

A

W=F.s

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5
Q

work done in circular motion

A

0

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6
Q

work done by gravity is

A

mgh from moving up to down

-mgh from moving down to up

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7
Q

work_total=

A

integration of f_net.ds

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8
Q

total work done by all forces is

A

work done by net force

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9
Q

work done by variable force is

A

integration of (fxi+fyj+fzk).(dxi+dyj+dzk)

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10
Q

if force acts in only x direction

A

displacement is only in x axis and W=integration(Fxdx)

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11
Q

if F=f(x)

A

W=integration of f(x)dx from x1 to x2

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12
Q

work done by spring force

A

1/2kx1^2-1/2kx2^2

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13
Q

what are the limits of integration in compression

A

from 0 to -x

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14
Q

work done in a different frame of reference

A

integration of F.ds(in the frame of reference)

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15
Q

total work done by all forces

A

total change in kinetic energy

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16
Q

if 2 different springs (not attached to each other) is acting on a body

A

k_equivalent=k1+k2

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17
Q

if 2 different springs (attached to each other) is acting on a body

A

1/k_eq=1/k1+1/k2

18
Q

what is the work done by a system of bodies

A

total change in kinetic energy of system of bodies

19
Q

what is a conservative force

A

work done is independent of path and only depends on initial and final points

20
Q

what is a non-conservative force

A

work done is dependent of path

21
Q

what is potential energy

A

energy possessed by virtue of position

22
Q

when does potential energy change

A

only when conservative force does work

23
Q

formula of potential energy

A

-(work done by conservative force)

24
Q

where is the potential energy 0

A

the potential energy is 0 at the reference point

25
whAT IS principle of conservation of mechanical energy
Uf+KEf=Ui+KEi
26
what is mechanical energy
U+KE
27
what is work done by non conservative and external forces
change in mechanical energy
28
how to find fx fy and fz
partially differentiate U wrt dx dy and dz respectively
29
eg if U=3x^2yz find fx,fy and fz
fx=6xyz fy=3x^2z fz=3x^2y
30
whats stable equilibrium
its a position where the body shows tendency to the equilibrium upon being disturbed from equilibrium
31
whats unstable equilibrium
equilibrium position where the body shows tendency to move away from equilibrium upon being disturbed
32
whats neutral equilibrium
equilibrium which is neither stable nor unstable
33
at stABLE EQUILIBRIUM
PE IS MINIMUM
34
at unstable equilibrium
PE is maximum
35
how do you get to know if a body is in stable or unstable equlilbrium
dU/dx=0
36
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
37
what is power
rate of doing work
38
average power
work done/time interval
39
instantaneous power
dW/dt | F.v
40
total of average powers due to all forces on a body
change in ke by time
41
total of instantaneous powers due to all forces on a body
d(ke)/dt