$2\mathrm{.}71$ A bottle jack allows an average person to lift 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 vernal perception that you cant get something for nothing $($a somewhat loose paraphrase of the first law of thermodynamics$).$ Hint: Consider the work done by each force.