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igcse physics notesprinted 53 · PDF 53
124 pagesrevision 46936
printed 53 · PDF 53
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53
Answers:
1)
(c)(i) As the ball falls to the bottom, all the GPE is changed to other forms of
energy so initial total GPE= total GPE transferred
ΔGPE= mgΔh
ΔGPE= 2.1/1000 x 0.80 x 9.81
ΔGPE= 0.01648… ≈0.016J OR 1.6 x 10-2J
(ii) Kinetic Energy=
1
2mv2
K.E= ½ x 2.1/1000 x 1.22
K.E= 1.5 x 10-3
(iii) While falling down, some energy is dissipated as heat/sound due to work
done against drag, so not all the GPE is transferred to K.E.
2)
(a) Statement: It is renewable.
Explanation: More crops can always be grown by the farmers and
they will continue producing waste materials.
(b) (This part is more related to thermal physics). It is possible that the water may
cool down as it is transported long distances so some thermal energy will be lost.
To prevent this, we can insulate the pipes(or any vessel) in which the water is
transported to prevent any loss of heat.
3)
Gravitational Potential Energy (because water is stored at the top of the dam and
when it falls the GPE is converted to K.E of moving water which then pushes and
rotates the turbines to produce Hydroelectricity).
(b)(i) Rate of Energy Transfer = Power
Power= Energy/Time
Energy of falling water= G.P.E of water, G.P.E= mgh
E=mgh
Power= (410 x 9.81 x 480)/Time
Power= 1.930… x 106J/s ≈1.9 x 106/ 1s