Energy, Work & Power

1) A small car might have an engine that can produce 125 horsepower. Convert that to Watts, using the method shown in class.

2) Seventy-five pounds is equal to 330 Newtons. How much work is needed to lift a seventy five pound weight 1.5 meters? Show the equation, units, sig figs, etc.

3) Let’s say a weightlifter lifts 610 N 2.25 m in 1.2 s. Calculate the power.

4) Which takes more work, lifting a 84 N object 1.0 m in 2.0 seconds, or lifting the same 84 N object 1.0 m in 3.0 seconds?

5) Define temperature, using a strict definition.

6) Define calorie (not Calorie).

7) Here’s a problem where you need to consider those basic energy laws. In the real world (not the imaginary world of textbooks) if you were to lift an 80 N box 2 m, would you do more or less than 160 Joules of work? Why?

8) You picked up a 140 N box and put it on a table 1.1 m high, doing 250 J of work. Your friend did put the same box on the same table and did 290 J of work. It’s the same weight lifted the same distance! Why did your friend need to do more work?