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Physics Help HERE ONLY !!

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samin6n:
ok then...Thanks!...and thnk god!!i thought ppl are dead here!!!!

bball92:
lol im sure ppl r revising atm, i am doing past papers from 2002 till 2008 rite now :P and just tooka short break to post here =)

lana:
hi ... !! ok i have two questions it's from past papers June and November 03 :

1- the mass of a full bottle of cooking oil is 1.3 kg when exactly half the oil is used  the mass of the bottle and the remaining oil is 0.9 kg what is the mass of the bottle ? now i know it's ''B'' but how ??

2- the half life of a radioactive substance is 5 hours a sample is tested and found to contain 0.48 g of the substance how much of the substance was present in the sample 20 hours before the sample was tested ?? i also know its ''D'' but again how ??

thanks and +rep for anyone who answers =]

hmh:

--- Quote from: lana on June 09, 2009, 09:44:13 pm ---hi ... !! ok i have two questions it's from past papers June and November 03 :

1- the mass of a full bottle of cooking oil is 1.3 kg when exactly half the oil is used  the mass of the bottle and the remaining oil is 0.9 kg what is the mass of the bottle ? now i know it's ''B'' but how ??

2- the half life of a radioactive substance is 5 hours a sample is tested and found to contain 0.48 g of the substance how much of the substance was present in the sample 20 hours before the sample was tested ?? i also know its ''D'' but again how ??

thanks and +rep for anyone who answers =]

--- End quote ---

OK so 1 is B i dnt knw the value  1.3- 0.9 = 0.4 * 2 = 0.8 ... we got 1.3 - 0.8 = 0.5 kg as  0.5 kg mass of bottle.

2 .. again didnt look at the paper.. but guessesing tht answer shd be 7.68g... as 4 half lives reversed as of 5 hrs 1 time.. so 0.48*2*2*2*2 = 7.68.

MR.BooMBastiC:
da ist ans is .50kg

the second is 7.68

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