Ok, here's the question...
"A child can throw a baseball at 20mph. Some pro ball players can throw a baseball at 100mph, which is five times as fast. How much more energy does the pro ball player give to the faster ball?"
Since the ball is in motion, should I use the equation for Kinetic Energy (which is KE =1/2mass x speed^2)
2006-09-02 14:04:03 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Other people have already given you the correct answer, I just wanted to phrase it in a different way for you - which ever way makes more sense to you, stick with it.
You already noted the pro throws five times faster. Since KE depends on the speed *squared*, the pro's KE is 5^2 times (25 times) greater.
Of course you can also make up a mass and then calculate the individual KEs and then compare the two, but to me that's more work than you need to do.
2006-09-02 14:23:51 · answer #1 · answered by kris 6 · 1⤊ 0⤋
Yes...use the eqn for both 20 and 100 mph...then subtract then results to get how much more energy the pitcher is required to have to throw the ball at 100 mph vs. 20 mph.
By the way...kinetic or potential...at the instant the ball leaves the pitchers hand, both are the same. One instant it was potential...the next kinetic. Your method above is in the kinetic domain...ball in motion. Without friction or rotation...KE would be constant.
2006-09-02 14:13:16 · answer #2 · answered by BowtiePasta 6 · 0⤊ 0⤋
KE(Pro) = (1/2)*m*(100^2)
KE(Child) = (1/2)*m(20^2)
Find the ratio: Pro / Child
= (1/2)*m*(100^2) / (1/2)*m(20^2)
=(100^2)/(20^2) = 10,000/400
=25 times the KE
2006-09-02 14:12:45 · answer #3 · answered by Anonymous · 1⤊ 0⤋
Yes. Use KE=1/2 mv^2 for this problem.
Another way to think about its use is to think about how much KE your car has going 30 mph vs 60 mph.
2006-09-02 14:14:22 · answer #4 · answered by Stan B 2 · 1⤊ 0⤋
25 is correct. The poster above has the correct way of looking at it!
-T
2006-09-02 17:29:31 · answer #5 · answered by tomz17 2 · 0⤊ 0⤋
he's throwing it five times faster silly.
2006-09-02 14:08:38 · answer #6 · answered by Backtash123 1 · 0⤊ 2⤋
yes, you are correct.
2006-09-02 14:10:20 · answer #7 · answered by pandora the cat 5 · 0⤊ 0⤋