The iPad1 only has half the RAM of the iPad2. So, to help alleviate the problem, it's a good idea - if this is a persistent problem - to free up some RAM before launching Safari. The easiest way to do this is to completely switch off the iPad - by pressing and holding the Power button until the slider control appears. This process causes the iPad's operating system, iOS, to 'reclaim' and consolidate 'lost' RAM and will therefore make the maximum amount available to Safari.
Tim