# There is question regarding relativity

1. Oct 27, 2014

### ghostinpants

If you had two shoes, an ordinary shoe and an “antishoe” made of antiparticles, and you
annihilated them together, by how far could you lift the entire US population? Assume
that each person weighs 600 N, that each shoe’s rest mass is 0.5 kg and that all energy
goes into lifting.

I really have no idea how to solve this problem。 plz help

My attempt:
total mass:0.5+0.5=1kg
According to the formula: E=MC*2
total energy:1x9x10*16=9x10*16J
total distance you can lift: 9x10*16J/1.8956x10*11 N (total mass of entire us population)

Last edited: Oct 27, 2014
2. Oct 27, 2014

### BvU

Hello pants, and welcome to PF :)

Problem solving starts with collecting some relevant equations. What have you got on offer in this context ?

Furthermore, PF rules dictate that you show an actual attempt at solution (otherwise we would be in trouble with all teachers all over the place). No problem: just fill in some numbers to see how far you can get on your own !

3. Oct 27, 2014

### ghostinpants

Hi Bvu, I just posted my attempt

4. Oct 27, 2014

### BvU

I think you're doing just fine. In fact, you've done the whole thing. Pretty hefty result, isn't it ?

By the way, I love the precision in this total weight ;) I think one digit (*) is enough here...

(*) i.e. round off the final result

5. Oct 27, 2014

### Staff: Mentor

The final result is missing and it would be useful to give the US population number you use, everything else looks fine (see BvU for the rounding issue).