Common Prob student encountered during O level ComS(Physics)
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Definition incorrect
Stated Kinetic Energy when the question ask for Potential Energy
Interprete incorrect Distance-time graph and Speed-time graph
Electrical Resistance ,R =VI
Diverging , Diminished , Enlarged couldnt see the difference after drawing the ray diagram as drawing incorrectly ..
More will be covered in the following threads ,and in greater details
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Hi,
Perhaps it would be helpful to provide more details like:
1. Original question to make clear the context;
2. Student's answer that was incorrect;
3. Explanation of the source of error;
4. Advice on how to correct the error.
Thanks.
Cheers,
Wen Shih -
A ball of mass 200g is thrown vertically downwards from a height of 3.2m
(a) Calculate the potential energy of the ball when it is 3.2m above the grounds
PE =mgh
=200 x 10 x 3.2
= 6.4J
(b) Calculate the speed of the ball just before it reaches the ground.
(1/2) mv^2 =6.4
0.5 x 0.2 x V^2 =6.4
V^2=64
V=8ms^-1
(c) State the acceleration of the ball when it is falling .
[Student tends to think the acceleration is 8m/s which is wrong.Because acceleration due to gravity is always constant ]
therefore g =10m/s
(d) Hence ,find the force acting on the ball as it is falling .
F=mg = 0.2 x 10 = 2N
[Note:when the acceleration of the ball is answered wrongly, naturally the answer of the Force acting on the ball will also be wrong ,as wrong value is used]
Source:Ahmad Ibrahim Secondary School ,GCE O level Prelim Exam 2008
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Give some question that u don't under stand, and i maybe able to help you with it
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Originally posted by Forums-ws:
Give some question that u don't under stand, and i maybe able to help you with it
Sorry to say ,I am a tuition teacher and thanks for the offer to help . -
