Question

In the decomposition of Th-90, the mass defect = 4.50 x 10^-24 kilograms. If all of this mass is converted to energy, what would be the value in joules? (1 J = 1 kg m2/s2)

A) 4.05 x 10^-7 J
B) 1.50 x 10^-8 J
C) 1.35 x 10^-16 J
D) 5.4 x 10^-32 J

Can anyone help me figure out how to solve this problem??

Answer 1

E=mc^2

Answer 2

so E= 4.50 x 10^-24 / 3.00 x 10^8 ? And then I convert the answer to joules? Or do I have the formula wrong...

Answer 3

nope, it's multiplied

E=(4.50 x 10^-24)(3.00 x 10^8)^2

Answer 4

So 4.50 x 10^-24 * 3.00 x 10^8 = 1.35 x 10^-15.
(1.35 x 10-15)^2 = 1.8225 x 10^-30. Does that look correct? I have to convert that to joules once I get the answer.

Answer 5

you are only supposed to square the 3.0 x 10^8 NOT the result......that is why you are getting the answer wrong....

Answer 6

ohhh ok i see

Answer 7

so do you get the answer??

Answer 8

I got 0.000000405 :P

Answer 9

nooo.....did you input the right values on your calculator??

Answer 10

Wait nevermind I got 1.35 x10^-15

Answer 11

i did not get the same value...

Answer 12

I'm confused then :(

Answer 13

can you type the values you used for the calculation??

Answer 14

4.50 x 10^-24 * 9.00 x 10^16

Answer 15

can anyone help me

Answer 16

if that is exactly what you typed, you should be getting
4.05 x 10^-7

Answer 17

huh. I don't know what I'm doing wrong then

Answer 18

i've tried the same calculation a dozen times and still get the same answer :/

Answer 19

http://www.wolframalpha.com/input/?i=4.50+x+10%5E-24+x+9+x+10%5E16

Answer 20

oh alright I guess I was just going wrong somewhere. So now I convert that joules.

Answer 21

no..that is it...its already on joules....

Answer 22

ohhh okay. Well thank you for helping :)

Answer 23

you are welcome...
if you are given a question next time with the mass in grams, you would have to convert it into kilograms first....then after that your energy calculated would be in joules..

Answer 24

Alright that makes sense. Thanks