Mass Weight Thrust Pressure and Relative Density NCERT

Mass- The mass of the body is the quantity of matter (or material) contained in it.

  • mass is the scalar quantity which has only magnitude but no direction
  • The SI unit of mass is kilogram.
  • Mass of a body is a measure of inetia of the body.
  • The Mass of a body cannot become zero.

Weight-The weight of a body is the force with a certain force which depend on the mass of the body and acceleration due to gravity at that place.

Force = Mass X Acceleration due to gravity

Force= m X g

hence W= m X g

Thus the weight of 1 kg mass is 9.8newton. This means that the force acting on a mass of 1 kg at the surface of the earth is 9.8 newtons.

  • Weight is a vector quantity
  • The weight of the body changes from places to place
  • In space the alue of g = 0 . hence Astonaut feel weightlessness in space.
  • The Weight can be Zero.
  • A spring balance can show the weight of a body


Weight of an object on the moon

  • As the value of g is 1/6 times than that of earth.
  • So the weight of an object will be 1/6th of the weight as on the earth.

Consider  this Example.

If the weight of a Boy is 504 Newton on the surface of the earth. what will be the weight on the surface of the moon.

As Weight is 1/6 times on the surface of moon.

So The weight will be 504/6 = 84 Newton on the surface of the moon.


Difference between Mass and Weight

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