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Matter In Our Surroundings

Question
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Define kinetic energy and potential energy. Write an expression for the kinetic energy of a body of mass m moving with a velocity v. Find the kinetic energy of a body of mass 40 kg moving with a velocity 15 m/s.

Solution

Kinetic energy: Energy possessed by a body by virtue of its motion is called its kinetic energy.

Mathematically, kinetic energy is expressed as, 

                       K.E  = 12mv2 

where, 

m is the mass of the moving body,
v is the velocity of the body.

Potential energy: Energy possessed by a body by virtue of its position or shape is called its potential energy.

For a body of mass m lying at a height h above the ground level, gravitaional potential energy is given by, 

                         P.E = mgh 

Given,

Mass of the body, m = 40 kg
Velocity of the body, v = 15 m/s

So,  K. E. = 1 mv2  = 1 x 40 x (15)2 = 4500 J.
                  2             2

Some More Questions From Matter In Our Surroundings Chapter

Convert the following temperature to Celsius scale.

573 K

Convert the following temperatures to Kelvin scale

25°C

What is the physical state of water at

100 °C

For any substance, why does the temperature remain constant during the change of state ?

Suggest a method to liquify atmospheric gases.

Convert the following temperatures to Kelvin scale.

35°C

Give reason for the following observations.

Naphthalene balls disappear with time without leaving any solid.

Give reason for the following observations.

We can get the smell of perfume sitting several metres away.

What is the physical state of water at

a) 25°C
b)00C
c)1000C

What is the physical state of water at
0°C

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