Final answer:
To apply a nut to a bolt that is difficult to spin with fingers, you can use a power drill or a socket wrench, which provides the mechanical advantage needed for the task. Mechanics also use a length of pipe for extra leverage, which increases torque but can potentially break the bolt.
Step-by-step explanation:
To drive or run a nut onto a bolt that resists spinning it on with fingers, you can drive the socket with a power drill or socket wrench.
When you use a socket wrench or power drill, it provides the necessary grip and mechanical advantage to apply torque to turn the nut. Turning the wrench clockwise will tighten the nut while turning it counterclockwise will loosen it. This use of tools exemplifies the principle of torque, a concept in physics that describes the rotational force applied to an object.
Mechanics may also use a length of pipe over the handle of a wrench to remove a very tight bolt, which effectively increases the torque due to the increased leverage. However, this can be dangerous as it might break the bolt if applied excessively.
The torque τ is calculated as the vector product of the radial distance R to the point where the applied force F acts: τ = R × F. For example, if a mechanic needs to tighten cylinder head bolts with a specified torque of 62.0 N.m using a wrench of length 20 cm, the mechanic must apply a perpendicular force at the end of the wrench calculated based on the torque and length of the wrench.