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PHYSICS 31 doubts plzzz clear :P

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For the first link, it's effiency is 10%. Therefore you calculate the total energy it produces, and divide it by 10. Since the previous figure in 5(a)(i) is in 1 second, there is no need to divide the answer by time. (actually there is, but anything divided by 1 is the same) For part (b), I think that since the speed is half, the mass of air travelling in one second is halved as well. For (ii), since mass is halved, and speed is halved twice (1/2 x m x v^2), it would be divided by 8. Therefore, 12.5%.
 
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For the second link, since there's no aiii, i'm assuming you mean b(iii). Well, it's pretty simple. Due to the formula p1v1=p2v2, we can say that it applies for the bubble as well. So at the bottom, the bubble has a specific volume, and there is a specific pressure at the bottom of the pool. When you reach the surface, the pressure decreases, so the volume of the bubble would increase.

6a. Proton number must always be equal, since isotopes are atoms of the same element with a different amount of neutrons.

b. 120 -> 60 -> 30 -> 15
Therefore, it decays three times, so times the half-life by 3.
ii) It's fact that when atoms decay, they release alpha/beta radiation. Therefore, they can change in their total proton number/nucleon number. Therefore, they may change into an isotope.

iii) It has an EXTREMELY long half-life, so unless we're testing it for 1000000 years, its decay will not have a significant impact on the experiment.
 
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Last link, Q11 - Same thing, nucleon numbers - proton + neutron. Though nucleon number may change, proton number WILL always stay the SAME!
Any practical use, such as gas leakage detectors and cancer treatment and paper thickness control.

Q7- a) For the mirror, it reflects. For the glass block, it penetrates and refracts(towards the normal). As you know, it slows down in denser mediums, so the wavelength will lessen.

b) Basic calculations involving sin i/ sin r and speed in air/ speed in block.

Q10- They involve control circuits. Whenever you see OR in the phrase, it involves an OR gate. AND = AND gate. Be sure if you have time in your exam to CONFIRM your answers, since everyone can make a mistake. Do ensure that it works for all inputs.
 
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Physics: when temperature is increased, volume is also increased but pressure is kept constant........how can pressure be kept constant because when temperature is increased the gas molecules will hit the molecules with greator force so eventually pressure would be increased......how can pressure be kept constant??
 
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