Einstein's formula (E=mc^2) tells us how much energy is emitted when mass is annihilated, where E is energy (in joules), m is mass and c is the speed of light (3 x 10^8 m/s).

A penny has a mass of 2.35 g. How much Energy would be produced if it was converted into energy? The final answer must be in kWh

Question

Einstein's formula (E=mc^2) tells us how much energy is emitted when mass is annihilated, where E is energy (in joules), m is mass and c is the speed of light (3 x 10^8 m/s).

A penny has a mass of 2.35 g. How much Energy would be produced if it was converted into energy? The final answer must be in kWh

jamesj · Answer

E = mc^2
   = (2.35 )( 3 x 10^8)^2 J

Now, Power = Energy/Time
         1 Watt = 1 Joule/1 sec = 1 J/s

hence 1 Watt.hour        = 1 Wh  = 60^2 J/ = 3,600 J
          1 kilo Watt.hour = 1 kWh = 1000 x 3,600 J = 3,600,000 J

So once you've found the energy above, divide it by 3,600,000 to express it in kWh.

jamesj · Answer

Make sense?

anonymous · Answer

yep. tnx ;)

anonymous · Answer

you should convert g to kg into so, 2.35 g=0.00235 kg

jamesj · Answer

That's correct.  So the energy is
E = mc^2
   = (0.00235 )( 3 x 10^8)^2 J

Thanks for the catch.

anonymous · Answer

E=2*10^14 J

1J=3*10-7 kWh 

so $$E \approx 6*10^{7} kWh $$

anonymous · Answer

1J=3*10^-7 kWh