# Warm-Up Exercise for lecture 10

## Due 8:00 am, Thurs, Oct 2

Physics 105, Fall 2008

A good, professional baseball pitcher throws a ball straight up in the air. Estimate how high the ball will go if he can throw as hard vertically as he can horizontally. ( A good pitch can reach about 90 mph = 40.2 m/s.)
☐ 0-20 m
☐ 20-40 m
☐ 40-60 m
☑ higher than 60 m

You compress a spring 10 cm from its equilibrium position. Then you compress it another 10 cm. In which step did you do more work?
☐ The first 10 cm
☑ The second 10 cm
☐ Both cases involve the same amount of work.

You need to carry a suitcase up a flight of stairs. In which case will you expend the most power?
☑ You carry the suitcase up quickly.
☐ You carry the suitcase up slowly.
☐ Both cases involve the same amount of power.

One farmer is bragging about his strong horse, his neighbor is proud of his powerful horse. If these men are giving the words "strong" and "powerful" their correct physics meanings, what can you say about the two horses?

"Strong" probably means that the horse can exert a large force. It could e.g. drag a large load (but it doesn't say anything about for how long). "Powerful" means that the horse can do a lot of work (force x distance) per time.