# Homework Help: Energy causing motion

1. Nov 7, 2008

### starfox07

Hey all,

1. The problem statement, all variables and given/known data

"Suppose that we could use the energy released
when 4 g of antimatter annihilates 4 g of
matter to lift a mass 1 km from the Earth’s
surface.
How much mass could we lift? Answer in
units of kg."

2. Relevant equations

e=mc^2
w=fd
f=ma

3. The attempt at a solution

I was attempting to find the energy with e=mc^2 and using .004kg as the mass. Then I tried using work(energy)=force*distance and force=mass*acceleration (using gravitational potential energy) but my answer was incorrect. For the record, i answered 3.67e10 kg but no luck. I'm stumped. :(

EDIT: I think the proper way is using the potential energy equation [energy=mass*gravity*height] after I have found energy from [e=mass*speed of light^2] Is this right?

Would the total energy released be from .004kg or from .008kg of matter?

Last edited: Nov 7, 2008
2. Nov 7, 2008

### krausr79

I'll take a stab at it. According to http://en.wikipedia.org/wiki/Antimatter_weapon the amount of energy produced by a gram of antimatter is 180 Tjoules, which is twice the amount predicted by your method. It may be since both matter and antimatter are being destroyed you must double the mass in E=mc2. Perhaps if you doubled your answer?

3. Nov 7, 2008

### starfox07

Let me see if that works..

4. Nov 7, 2008

### starfox07

wohooo thats it!! thanks a bunch

Interesting to note that just 4 grams of anti matter (like the weight of a pen) can move 81 million tons of *whatever* more than half a mile vertically.

Last edited: Nov 7, 2008