Question

Define kinetic energy. obtain an expression for the kinetic energy of an object

Answer 1

energy which a body possesses by virtue of being in motion.

Answer 2

Hello friend
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Let's start,

Definition: The energy which an object has because of its motion is called it's kinetic energy.

Suppose a stationary object of mass m moves because of an applied force.Let u be its initial velocity (here u = 0).Let the applied force be F . This generates an acceleration a in the object,and after time t, the velocity of the object becomes equal to v. The Displacement during this time is s. The work done on the object,

W = Fs

W = F x s

So,according to Newton's second law of motion,

F = ma. ............(1)

Similarly,
using Newton's second equation of motion

s = ut + 1/2 at^2

s = 1/2at^2 .....................(2)

W = ma x 1/2at^2. .......(using equation (1) and (2)

W = 1/2m x (at)^2 .............(3)

Using Newton's first equation of motion

v = u + at

v = 0 + at

v = at

v^2 = a^2 t^2 = (at^2).........(4)

W = 1/2mv^2 .........(using equation (3) and (4)

The kinetic energy gained by an object is the amount of work done on the object.

hence,

K.E = W

K.E = 1/2mv^2

Now take an example based on Kinetic energy.

eg.. A stone having a mass of 250gm is falling from a height.How much kinetic energy does it have at the moment when it's Velocity is 2m/s.?

=) Given :

Mass of the object,m = 250g
mass is given into gram so we will write it into kg.

So 1 kg = 1000g.

m = 250/100 .

Velocity of the object = 2m/s.

We have to find, the kinetic energy of the object,

So,we know that,

Kinetic energy. = 1/2mv^2

By putting the values,we get


kinetic energy = 1/2 x 250/1000 x (2)^2

kinetic energy = 25/100 x 2

kinetic energy = 50/100

kinetic energy = 0.5 J.

I hope this will helps you.

Thanks .