Question

why do we use a long handle with a screw jack

Answer 1

The jack screw provided with a long armbecause in order to produce maximum turning effect of the screw jack the force is applied at point of body for which the distance from the axis should maximum so that the given force provides maximum torque to turn the screw jack.

Answer 2

here is your answer.....
The jack screw provided with a long armbecause in order to produce maximum turning effect of the screw jack the force is applied at point of body for which the distance from the axis should maximum so that the given force provides maximum torque to turn the screw jack