Energy & Power Video Lecture | Physics for Class 9

hi it's mr. Andersen and today I'm going
to talk about energy work and power now
what's something that has energy that's
pretty big term so what things have
energy well we would say something in
motion or something due to its position
we could say that electricity is a form
of energy we could say that matter can
contain energy within its chemical bonds
or light has energy or sound has energy
so that's a lot of different things what
is energy energy therefore is the
ability to do work
well that's one of those definitions
that requires us to dig a little bit
deeper what is work work and science is
simply a force times a distance so
anything that can apply a force or over
a given distance is said to contain
energy and we measure that in joules so
work is measured in in joules and so
let's give an example let's say for
example that you want to take a can of
coke and you want to carry it to the top
of a set of stairs
well that can of coke has 4.0 newtons of
weight and let's say that you have to
climb up a set of stairs that is 3.0
meters high now the interesting thing is
that since the gravitational force is
always acting down it doesn't matter if
you get to the top of the stairs by
walking up stairs or get to a similar
distance by climbing up a ladder or
simply just throwing the can of coke up
to that point if you've moved it up a
certain amount of distance we'll call
that 3.0 meters then you've done 4.0
Newton's times 3.0 meters or 12 joules
of work to get that to the top now you
could get that to the top in a couple of
different ways let's say that we were to
gradually make our way to the top of the
stairs or we were to run up the stairs
well we would be doing the same amount
of work depending on if we're running or
going slowly and so we need another term
to figure out how fast we're doing that
and that's called power and so power is
defined as the amount of work in a given
period of time and let's say so let's
say that you were to go up that set of
stairs with
Tanna coke and you were to do that in
one second
well the amount of work we have is going
to be 12 joules and the amount of time
is going to be one second and so the
power of that is going to be 12 watts or
w80 TS or watts is going to be the
amount of power that we have if you do
that slower so let's say we were to do
that in 10 seconds then the amount of
watts would drop from 12 watts to 1.2
watts so that's that's really not that
much power and so the amount of power
that we're actually used to dealing with
here in the u.s. is horse power and so
horse power is measured it measures the
amount of work that we can do in a given
period of time we use it in engines for
example and so the conversion is 1
horsepower is roughly 746 watts and so
let's go back to that problem if we're
able to move a can of coke to the top of
the stairs in one second we say that
that's a 12 Watts on so if we convert
that to horsepower than we are at point
zero zero four horsepower machine so
that's not a very powerful machine now
the one thing that you should realize is
not only are we moving that can of coke
to the top of the stairs but we're also
moving our weight our whole body to the
top of the stairs and so maybe we're a
little more powerful than we think