The Energy of Railgun's projectile

1. Jan 25, 2016

Yongho Ahn

I'm making a simple railgun.
and I'll charge capacitors(330v, 1000uF) for railgun's power source.
but I just have a question. the railgun's projectile is about 20g, and rail is about 20cm(height)
how can I get the projectile's speed(in end of the rail)?
or projectile's kinetic energy?
(don't mind something else : frictional force or etc. just Electrical Energy to Kinetic Energy)
somebody help me :)

2. Jan 25, 2016

Staff: Mentor

If you could convert all the electric energy to kinetic energy, you could just look up the formulas for energy stored in capacitors and for kinetic energy, and solve for speed and kinetic energy. This will vastly overestimate the actual result, however, and getting a precise estimate is really challenging.

3. Jan 25, 2016

Yongho Ahn

Then, How can I get a losing energy(frictional or else other)?
In my calculation, the charged energy is about 54.45J(Elec.)
And according to your reply, the projectile's kinetic energy is very small. right?
My purpose : I just thinking about just (kinetic energy, projectile)10J or over.

4. Jan 25, 2016

Staff: Mentor

With a detailed simulation of your setup, which is probably beyond the scope of the project.

5. Jan 25, 2016

Staff: Mentor

You can also check the numerous other home made railgun projects, many of which are documented on Youtube.

Note that the energy of that railgun was 27,000 joules.

6. Jan 25, 2016

Staff: Mentor

Looks kinda dangerous to me...

7. Jan 25, 2016

Jeff Rosenbury

Rail guns are inefficient. Lots of energy ends up heating various components through eddy currents and the like.

Your best bet is to measure the muzzle velocity. Then you will know the exact kinetic energy.

To do this you will need a chronograph. They sell for about \$150, or you could build your own. Building your own would be both more useful and safer than a railgun.