Final answer:
The long handle on a jar-opening tool provides greater leverage, making it easier to apply the necessary torque to the lid to open the jar. It is a fundamental application of physics where a longer distance from the pivot point allows the application of less force to achieve the same result.
Step-by-step explanation:
The length of the handle on a jar-opening tool assists in opening a jar because it provides greater leverage. Leverage here refers to the mechanical advantage gained by using a tool to multiply the force applied to another object. In this case, when you turn a longer handle, it enables you to apply more torque to the lid, which is the rotational equivalent of force. This happens due to a principle in physics wherein the longer the distance from the pivot point (which is where the lid twists off), the less force you need to apply to achieve the same amount of torque. Therefore, the longer handle reduces the effort required to open the jar.
Mechanics using a length of pipe over the handle of a wrench to remove a very tight bolt is a similar example of increasing leverage. By adding the pipe, they increase the effective length of the wrench handle, therefore requiring less force to produce the necessary torque to turn the bolt, albeit increasing the risk of breaking it.