A bottle jack allows an average person to lifi one corner of a 4000 -lb automobile completely off the ground by exerting less than 20 lb of force. Explain how a 20 -lb force can be converted into hundreds or thousands of pounds of force, and why this does not violate our general perception that you can't get something for nothing (a somewhat loose paraphrase of the first law of thermodynamics). Hint: Consider the work done by each force.

A 20 lb-force can lift thousands of pounds thanks to the principles of mechanical advantage and the conservation of energy, as illustrated by the function of a bottle jack. The tool amplifies the applied force by transforming a small movement in a region of small force into a large movement in an area of high force. The force exerted at the small piston is amplified at the large piston due to the difference in the areas. However, the first law of thermodynamics ensures that energy is not created but rather transformed: the work done by the individual is equivalent to the work done by the jack, with the amplified force compensated by a smaller movement distance. The user isn't getting 'something for nothing' but is effectively applying the principles of physics to accomplish the task.