what explains the fact that a small force can lift a car in gasoline stations?

Answer 1

In hydraulic lift there are two pistons connected to the system of common hydraulic liquid, one having smaller diameter, r, and the other having a larger diameter, R. When force, F, is applied to a piston with smaller diameter, it results in a pressure = F / πr^2. This pressure is transmitted through hydraulic liquid to the larger piston and the force that gets applied on it
= pressure * area
= (F / πr^2) * (πR^2)
= F * (R/r)^2.
Thus, it can be seen that a force F is increased by a factor of square of the ratio of radii of the larger and the smaller piston which becomes very high as compared to the applied force F.
For figure and better explanation, you can refer to my free educational website www.schoolnotes4u.com Physics Theory -XI chapter on fluid mechanics. You can also download study notes of physics and mathematics from the website without requiring any registration.

Answer 2

fL = Fl; where f is the small force acting over a long lever L and F is another force acting over a short lever l. This is like a teeter totter with a light person f sitting way out on the end L distance from the fulcrum.

At the other end a fat person F is sitting a distance l closer to the fulcrum. The two people balance out and the teeter totter stays horizontal because of something called mechanical advantage.

So we have F = (L/l) f and (L/l) > 1 is the mechanical advantage of the teeter totter allowing the fat person F and the skinny one f to balance each other even though F >>> f.

The hydraulic system of the lift in a gasoline station also has mechancal advantage. For example, if a small compressor can exert a 100 pound force f on a hydraulic system with a (L/l) = 100 times mecahnical advantage, we see that F = (L/l) f = 100X100 = 10,000 pounds. The lift can lift (what else) 10,000 pounds of vehicle, more than enough to hoist a car even though the compressor generated only 100 lbs of force.

And that's your answer. A hoist can lift a car in a gasoline station because of its mechanical advantage, which allows just a small force to lift a big weight. By the way, to lift F just a little bit (l), the small force f has to move a long distance L. That's because FXl = fXL to balance; so that the large force moves just a short distance to balance out the small force moving a large distance.

You can find mechanical advantage in a number of common systems. Winches and pulleys, for example, have mechanical advantage. Teeter totters, as we saw earlier, have mechanical advantage depending on where the two riders sit. Hydraulic brakes also have mechanical advantage. But they all operate on the same principle...leverage.

Answer 3

Hydraulics, whose underlying principles are explained with Bernoulli's Equations.

Answer 4

Energy shouldn't be seen from a thing's size. Heard of Atomic Bomb ?

Answer 5

hydraulic pump.

Answer 6

hydraulics.