1.A lever does 765 J of work and the person using the lever applies 900 J of work. What is the efficiency of the lever? 2.When your car gets a flat tire, you need to use a jack to lift the car. The car requires only 9000 J of work to lift it, but due to the inefficiency of the jack, you need to put in 15,000 J of work to lift the car. What is the efficiency of the jack?

3.An automobile gasoline engine can do 225 J of work with each stroke of its pistons. If the engine has an efficiency of 30%, what is the amount of work that must be done on the pistons in the engine?