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The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan Weight and mass.

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Presentation on theme: "The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan Weight and mass."— Presentation transcript:

1 The Professional Development Service for Teachers is funded by the Department of Education and Skills under the National Development Plan Weight and mass T.H.

2 PDST Resources for Leaving Certificate Physics 2 What units are used by this weighing scale?

3 PDST Resources for Leaving Certificate Physics 3 The scale on the left uses newtons. The scale on the right uses kilograms (in red) and stones (in black). Compare the readings.

4 PDST Resources for Leaving Certificate Physics 4 Newtons are much smaller than kilograms. How many newtons are there in a kilogram?

5 PDST Resources for Leaving Certificate Physics 5 It depends what planet you’re on! On earth, 1 kg has a weight of 9.8 N On the moon, 1 kg has a weight of only 1.6 N

6 PDST Resources for Leaving Certificate Physics 6 On Earth Sean reads 69 kg or 676 N.

7 PDST Resources for Leaving Certificate Physics 7 On the moon, Sean would still have a mass of 69 kg, but his weight would be only 110 N. So, one way to lose weight is to go to the moon.

8 PDST Resources for Leaving Certificate Physics 8 Is mass the same as weight?  What’s your opinion?  Can you think of any differences between the two quantities?

9 PDST Resources for Leaving Certificate Physics 9 Mass and weight  The weight of an object is due to the force of gravity acting on it. It is measured in newtons. A body’s weight can change depending on whether it’s on earth, the moon, mars and so on.  Mass is measured in kilograms. According to one definition, it is a measure of the resistance of a body to motion. Unlike your weight, your mass won’t change if you move to another planet.

10 PDST Resources for Leaving Certificate Physics 10 W = mg  Weight = mass multiplied by the acceleration due to gravity  Jane has a mass of 58 kg. Find her weight on each of the following: EarthMoonMarsJupiterSun g / m s –2 9.81.63.7125.95274.13

11 PDST Resources for Leaving Certificate Physics 11 Answers

12 PDST Resources for Leaving Certificate Physics 12 A Final Question  Is g = 9.8 m s –2 everywhere on earth?

13 PDST Resources for Leaving Certificate Physics 13 Answer  No. Comparing cities, it is lowest in Mexico City (9.779 m s –2 ) and highest in Oslo (Norway) and Helsinki (Finland) (9.819 m s –2 ).  Standard gravity, or standard acceleration due to free fall, usually denoted by g 0 or g n, is the nominal acceleration of body in a vacuum near the surface of the earth. It is defined to be precisely 9.80665 m s –2.


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