In order to prevent pregnancy would just condoms work?

Mostly, but not 100%: Several studies have shown that condoms alone, when used properly, still result in 2% pregnancies (i.e. If 100 women had male partners that used condoms properly, two of them would still get pregnant). Unfortunately, condoms are often not used properly, and 18% of condom users still get pregnant, largely due to incorrect condom use. (the percents i quote varies depending on many factors.).

Condom: Good answer by Dr. Rosenthal. Here is a great article about how to maximize efficacy of condoms. See: http://www.livescience.com/18661-14-common-condom-errors.html When used consistently and correctly there can be 98% efficacy.