can i safely use a 60 w adapter on a 2009 macbook pro computer
For future reference, providing the exact model of your computer will be very helpful in getting accurate advice. In 2009 Apple actually released five different MacBook Pro models. See below for the power adaptor used with each model:

MacBook Pro 17" early-2009 -
(85W MagSafe Power Adapter)

MacBook Pro 13" mid-2009 -
(60W MagSafe Power Adapter)

MacBook Pro 15" mid-2009 (2.53GHz model) -
(60W MagSafe Power Adapter)

MacBook Pro 15" mid-2009 -
(85W MagSafe Power Adapter)

MacBook Pro 17" early-2009 -
(85W MagSafe Power Adapter)

In a nutshell, your 60W adapter will work with both the MacBook Pro 13" mid-2009 and MacBook Pro 15" mid-2009 (2.53GHz model) computers. It should not be used with the others!

Hope this helps.