1. Power CHAPTER 5

2. Warm-up Which requires more work: lifting a one-kilogram mass two meters in one second or lifting a one- kilogram mass two meters in one minute? Explain your answer in words. Each situation required the same amount of work!

3. Don’t be tricked! Both tasks in the warm up require the same amount of work. Go ahead, calculate it— work has no dependence on time! “But how can this be?” you ask. “It’s harder to lift an object quickly than it is to raise it slowly!” What is different about the aforementioned tasks is the power developed in each.

4. Power

5. Which means that the power developed by a moving object can be calculated as the scalar product of the force acting on it and the speed at which it is being propelled.

6. Think about this one: if a 1 N (~0.1 kg) object were propelled along a frictionless surface at a speed of 1 m/s, how much power would be required?

7. Units

8. Two physics students, Will N. Andable and Ben Pumpiniron, are in the weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one minute; Ben lifts the 100-pound barbell over his head 10 times in 10 seconds. Which student does the most work? Which student delivers the most power?

9. An escalator is used to move 20 passengers every minute from the first floor of a department store to the second. The second floor is located 5.20 meters above the first floor. The average passenger's mass is 54.9 kg. Determine the power requirement of the escalator in order to move this number of passengers in this amount of time.