# Principle of moment in screwdriver

Can anyone help me to know why do we use screw driver of longer length of the wrench from the centre of the nut held between the jaws to the place on the handle where you pull (or push) on the wrench that is why do not we use screw driver with long handle as per this formula moment of force = F *r . i want to ask something this Torque, τ, equals r × F. Its magnitude is rF sin θ. Here, r is either the radius of the screwdriver handle or the length of the wrench from the center of the nut held between the jaws to the place on the handle where you pull (or push) on the wrench. F is the force you apply, and θ, of course, is the angle between the vectors r and F. For the screwdrivers, since you wrap your hand around the handle and turn the screwdriver, you apply the force at 90° to the radius of the handle. While it is possible to hold the wrenches at various angles, when you wrap your fingers around the wrench handle, the most natural angle at which to hold it is 90°. This, of course, maximizes the torque you can exert, and unless the nut or bolt you are trying to turn is in an awkward location, it is how you would normally apply force to the wrench handle.

As noted above, r is the radius of the screwdriver handle or the length of the wrench handle (from the center of the nut or bolt being turned to where you hold the wrench), so the larger the diameter of the screwdriver handle, or the longer the wrench handle, the greater the torque you can develop by applying a given force.

• This is really hard to read, it's one long sentence. It is also more of an engineering question IMO. – JMac Jul 4 '17 at 11:43
• There is no need to make a screw driver bigger than necessary (you need to be able to carry it) – Steeven Jul 4 '17 at 12:01
• It seems to me that OP is confused about what a "screwdriver" is. – Hot Licks Mar 30 '18 at 2:07