mysterymarkplz
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Not sure if space or motors.... (1 Viewer)
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hit patel
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Not sure of this is right but by the projectile formula (v^2-u^2)/2g = d we get v= sqrt (2gd) since u=0. By subbing in values u find v=sqrt (19.6). Now kinetic energy difference in values =KE= KEf-KEi: 1/2 * 0.1 ( 19.6 - 3.8^2) = 0.258. The solution is D?. note the KEi represents the value of kinetic energy resulting due to opposing of motion and the KEf is the energy the object falling would have possessed if there were no eddy currents i.e. if it wasnt a magnet. This is because law of conservation of energy and lenz law states that energy can be created or destroyed therefore the energy must be obtained from the kinetic energy of magnet to oppose the change in flux and motion of magnet. This kinetic energy is the energy converted to electrical energy by faradays law as you know. This is let off by the light assuming no resistive heat losses. Its both space and motors and generators. Hope that helps. Should be worth 2 marks!
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mysterymarkplz
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answer was B, teachers think the answer is C (i think) using 1/2 x mv^2
hit patel
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I must have done a lot of things wrong. i will check my work. But shouldnt the differences in kinetic energy be the energy that is converted to electrical energy? Maybe they took into account the exponential increase in induced kinetic energy over time due to intensity I which is propotional to 1/d^2 which applies to magnetic flux? Is this from fizzy?
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My answer is D. The KE gained by the magnet is lost in GPE.
Change in GPE = mgh = 0.98 J
KE = 1/2mv^2 = 0.72 J
Therefore, 0.26 J of the loss in GPE must have gone into electrical energy.
It's wrong as you pointed out but I'd like someone to tell me why.
Change in GPE = mgh = 0.98 J
KE = 1/2mv^2 = 0.72 J
Therefore, 0.26 J of the loss in GPE must have gone into electrical energy.
It's wrong as you pointed out but I'd like someone to tell me why.
mysterymarkplz
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you guys seem right, i think the answers are wrong.
hit patel
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? Sorry Didnt quite get the last sentence ...,. Yes I got d. My explanation was because if it came in a 3-4 mark question then it says with calculations explain then yeh my answer would be easily applicable, if correct.
But then why did the teachers answer c? and the answers say b? and we got d? there cant be 2 wrong answers"? may be this was Dr. ..... the phys teacher who did this incorrectly///
The magnet initially had 0 KE. It gained 0.72J in KE. But this must have come from GPE. However, it lost 0.98 J of GPE. Where did that extra 0.26 J go?