I’m looking for some scuba diving equipment that is good(meaning that it works) and isn’t too expensive. I need booties, fins, snorkel, & mask. What is a good brand to look at? Would oceanic be a good brand? or is there something a little cheaper? Thanks

As far as mask, fins and snorkel, the following link will help you to make an educated decision on the styles, features, benefits and drawbacks of those items. There are even videos on how to make sure you have the right fit. When you get to the main page just click on the "Read our Articles" link in the blue box.
http://www.snorkelingonline.com
If you are looking for scuba hard goods, Oceanic is an excellent choice. They are recognized worldwide so if you need anything serviced, you are bound to find a qualified retailer who can service the gear.
Check out
http://www.visibilityunlimited.com
for those items.
I know there is a 25% sale going on at the visibility unlimited site but you would have to e-mail to get the coupon code for the site
you can do that by e-mailing
info@visibilityunlimited.com and put what is the coupon code for the sale in the subject box.

from ebay for example, and how much should one pay for a full set

Not from ebay, I wouldn’t. You won’t know it’s service history or even able to have it reliably inspected prior to purchase.
Hit your local dive shops. A lot of dive shops have clubs. Many will have second hand gear that club members put up for consignment sales if they bought a newer bit of gear or they’ve outgrown their normal gear ( donuts will do that to you). Chances are pretty good that the shop will know the history of that gear because they will have serviced it for the seller. That shop will also make sure it’s safe and in good working order before even listing it for sale. It’s in their best interest to do that since they want you happy. Happy divers come back to the shop to buy more gear. Dead divers don’t.
A complete used gear package can go from a grand and up.That’s almost like asking how much to expect to pay for a used car. It depends on the car and it’s condition.
New gear and you can expect the price to start at around 1500 bucks all in. It only goes up from there. I’ve got about 30 grand invested in my two rigs for my recreational gear for example.
Edit: Tony is on my BS list. He likes to BS people and the guy has no idea of what he’s talking about. That would be why he is the only person I have blocked. Period. He’s not dead yet. He should be. He once advocated using a 32 % mix at 250 feet. Uhhh..right.

If the force on the tympanic membrane (eardrum) increases by about 1.50 Nabove the force from atmospheric pressure, the membrane can be damaged. When you go scuba diving in the ocean, below what depth could damage to your eardrum start to occur? The eardrum is typically 8.20 mm in diameter. Take the density of seawater to be equal 1.03\times 10^3 kg/m^3.

I tried to work out the length of a column of sea-water that is 8.2mm diameter and has a weight (force = mass x acceleration due to gravity) of 1.5 newtons.

The calculation came to 2.81m. That sounds about right, eh?

Working:

1. volume of a cylinder = (area of circle) x (length of cylinder).

2. area of a circle = pi x radius squared

3. diameter = 2 x radius

4. 1 meter = 1000 mm (8.2mm = .0082m)

5. mass of a solid = volume x density

6. force = mass x acceleration (due to gravity)

So:

Force = ( volume of column x density of sea water ) x g
1.5 = (pi x .0082/2 ^ 2) x depth x 1.03 x 10^3 x 9.81
1.5 = 0.533 x depth

depth = 2.81m