Home > categories > Automotive & Motorcycle > Car Lifts > Can someone explain to me how a car jack is able to lift a car and the physics behind it?
Question:

Can someone explain to me how a car jack is able to lift a car and the physics behind it?

I know torque is involved somehow but cant put it togethor.

Answer:

Mechanical advantage. For example, PA F and Pa f are the forces that can be generated with hydraulic pressure P throughout the car jack. A and a are different areas in the jack where the pressure is applied. So, on the manual end, you apply the force f to a small area and generate a pressure P f/a. Through Pascal's Law, that pressure transmits to the large area, A, under the car. And there you get PA (f/a) A f(A/a) F, a lifting force A/a times more forceful than your meager push f. A/a is the mechanical advantage. No torque here, just comparative areas for a common pressure. But a simple lever can do a similar thing, create mechanical advantage. And here the balance of torques can be used to show that. Mechanical advantage for a lever is (L - p)/p where L is the length of the lever and p is the distance from the short end to the pivot point. EX: If the pivot point of a see-saw is at p L/3, the mechanical advantage is 2/3//1/3 2. So a 75 lb kid on the long end could balance with a 150 lb adult sitting on the short one. Gears of different size can also be used for mechanical advantage. Again torque can be evoked to show that C/c is the mechanical advantage of a large gear with circumference C being turned by a small one of c circumference.

Share to: