I'm using a 9v battery via pack that plugs into power jack on arduino uno to power 5 servo motors and ping))) sensor through TinkerKit shield. When I plug the circuit in via computer they run fine, but when I power it through the battery pack the servos struggle to move. The battery is new and doesn'tr expire until 2018. Can I have some help!!! =( =( =( =( =( 
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If you are referring to a rectangular 9v battery with the two studs on the end - not enuff power. You need volts and amps. Those batteries have the volts but no amps at all and are practically useless for anything. Get a battery cradle that holds 6xAA, or better, 6xD
If you have a digital multimeter, check the amps on the 9v bateries.
Even if you use rechargeable AA bateries, they come with different amps.
Easy way: Use a baterry craddle as advised before (just for the sake of learning, measure the amps using the craddle, so you can have some grounds to compare).
Best way (includes a lot more, chargers) Lipo battery, the ones used in RC cars, airplanes.