Question

During times of dire emergency, people have been known to lift tremendous weights, such as the rear of a car to free a mechanic on whom the car has fallen. Is greater power necessary to perform such feats than when lifting the same car using a jack? Explain.

Answer 1

If any object is manually lifted, then greater power is required to lift the object.

But by using a jack, lesser power is required.

Work done = Force X displacement

Greater force is required to displace any object.

For a screw jack, rotational force (torque) is used.

The formula for torque is

`\tau=Force*\text{ distance from the axi}s`

Here, when we apply force by rotating such that its distance from the axis of rotation is maximum.

The concept here is torque is directly proportional to force applied and distance from the axis.

So, in order to minimize force, we can increase the distance from the axis.

Hence, we get more work done with lesser force.