Tuesday, 4 October 2016

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Physics: Mass and Weight, relationship, differences and related questions

mass and weight differences and relationship

A Taste of what you’ll Learn
                Basic definition of Mass

              Basic definition of weight

              Relationship between mass and weight

             Differences between mass and weight

             Related questions


A mass of a body is the quantity of matter contained in the body. It is scalar quantity I.e. it has magnitude but no direction. The unit of mass is kilogramme (kg).


This is a measure of the force of gravity of the earth on a body. It is a gravitational pull of the earth on any body towards its centre. It is a vector quantity I.e. it has magnitude as well as direction. The unit of weight is Newton (N).

Relationship between mass and Weight

Weight of a body = Force
Force = mass of body x acceleration due to gravity
I.e. W = F =  mg
m = W/g
For example: 

Find the weight of a ball if the mass of the ball is 10kg and the acceleration to gravity is 10m/s2.
W = mg
W = 10 kg x 10 m/s2
W = 100N

Difference between mass and Weight

1)  Mass is the quantity of matter contained in a body While weight is the measurement of the force of gravity on a body.
2) Mass is a scalar quantity while weight is a vector quantity.
3) The S.I. unit of mass is kilogramme while the S.I. unit of weight is Newton.
4) Mass of the body is constant throughout the universe, while weight varies from place to place in the universe.
5) The instruments  used to measure mass can be beam balance, lever balance or chemical balance, while the instrument used to measure weight is spring balance.

Mass and weight - on moon
    An astronaut on earth weighing 980N and mass of 100kg (acceleration due to gravity on earth is 9.8m/s^2).

Weight on Earth: 100kg x 9.8m/s2 = 980N.

The same astronaut on the moon would weigh 162.2N and have a constant mass of 100kg (acceleration due to gravity is 1.622m/s^2)

Weight on Moon: 100kg x 1.622 m/s2 = 162.2N.

Related Questions

1)  The mass of a rock on the Earth is 2.0 kg. What is the mass of the rock on the Moon?
A) 1.7
B) 2.0
C) 3.5
D) 20.0

2) Why is weight not equal everywhere?
A) Because of altitude.
B) Because of the varying mass other planets when compared with earth.
C) Because of force of gravity
D) All of the above
E) None of the above

3) An astronaut of mass 40 kg jumped out of the rocket after it had landed on Jupiter.  The astronaut took 0.40 s to drop for 2.0 m. What was the weight of the astronaut on Jupiter?
A) 500
B) 1000
C) 800
D) 2000

4) A student's weight on Earth is 100 pounds. If this student went to the Moon,what  would he weigh?
A) more
B) less
C) the same

Do you know any of the answers? If so share it or ask for it. Do you have any other mass and Weight related questions? Ask it and I will be happy to answer it or send you a detailed solution. Responses are within 24hrs.


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