Chp 2 Unit B Flashcards
(22 cards)
Two forms of mechanical energy
Potential and kinetic
Define potential energy
The energy possessed by a body at rest due to its position or size and shape is called potential energy
What is potential energy denoted by?
U
Two types of potential energy?
Gravitational (due to changed position) and elastic (due to changed size and shape)
Define elastic potential energy.
The potential energy possessed by a body in the deformed state due to change in its size and shape is called elastic potential energy.
Distance of the body from the surface increases, force of attraction ______ , gravitational potential energy _______
Decreases, increases
Define gravitational potential energy
The potential energy possessed by a body due to the force of attraction of Earth on it is called its gravitational potential energy.
Gravitational potential energy U at a height h=
mgh
If a body of mass M falls down from a height H1 to a height H2 about the ground the loss and potential energy:
H1 - H2 = mgh1 - mgh2 = mg (H1 - H2)
When a body of mass M is taken up from a height h1 a height H2 above the ground the gain in potential energy :
H2 - H1= mgh2 - mgh1 = mg (h2 -h1)
Define kinetic energy
What is kinetic energy denoted by
K
K =
1/2mv^2
Kinetic energy of a body is directly proportional to the
Square of velocity of motion
Relationship between kinetic energy and momentum
K = 1/2mv^2
P = mv
V= p/m
Mass increases, kinetic energy ?
Increases. (Assuming both bodies have the same momentum)
Mass increases, momentum?
Increases. (Assuming both bodies have the same K.I)
What is the work energy theorem?
According to the work energy theorem the increase in kinetic energy of a body is equal to the work done by a force acting in the direction of the moving body.
Write the W.E.T.
W = F.S
F = ma
V^2= u^2 + 2as
S= v^2 - u^2 /2a
Substitute in FS
ma * v^2 - u^2 /2a
m v^2 -u^2/2
mv^2- mu^2 /2
1/2 mv^2 - 1/2mu^2
But KIi = 1/2mu^2
And KIf = 1/2 mv^2
Hence W= KIf - KIi
W= increase in kinetic energy.
Distinction btwn kinetic and potential energy?
1) it is the energy possessed via body due to its changed position or size and shape
it is the energy possessed by a body due to its state of motion
2) it is equal to the work done and bringing the body to its changed state.
it is equal to the work that a moving body can do before coming to rest.
3) it can change only in the form of kinetic energy.
It can change into any other form.
4) it does not depend on the speed of the body.
It depends on the speed of the body.
Three forms of kinetic energy?
Translational, rotational, vibrational.
Loudspeaker?
Electrical to sound.
