math

A rubber ball dropped 80 feet rebounds on each bounce 3/5 of the height from which it fell. How far will it ravel before coming to rest?

😀

for all you smart fellers

320 feet?

It's a rubber ball, it won't ravel atall.


unless ravel means something different where you come from. 😛

Originally posted by Drew L
A rubber ball dropped 80 feet rebounds on each bounce 3/5 of the height from which it fell. How far will it ravel before coming to rest?

😀

for all you smart fellers

It wont "travel" as it was dropped from height, if it was dropped perfectly vertical, it will rest where it first bounced. (in theory!)

😉

Originally posted by smomofo
320 feet?

Horah!

320 feet it is.

Cool. I actually figured that out on my own! Thanks.

Originally posted by smomofo
Cool. I actually figured that out on my own! Thanks.

yeah, it was on my pre-calculus final.

A1 / 1 - r where A1 = initial drop and r = rate of rebound

First find the height of the first rebound

80 * (3/5) = 48

Second Use the geometric infinite geometric convergent formula [ once for the drop and once for the rebound, drop is given, step one finds the rebound]

80 / 1 -(3/5) = 80 / (2/5) = 80 * (5/2) = 200

48 / 1 -(3/5) = 48 / (2/5) = 48 * (5/2) = 120

Finally, add the two numbers together and there you have it.

I couldn't remember that stuff, so I just added the first few terms of (0.6) + (0.6)^2 + (0.6)^3 + ... and saw that it was headed for 1.5 and went from there. Maybe not the way it's supposed to be done, but I bet I could have faked my way to a decent mark on that question.

Originally posted by smomofo
I couldn't remember that stuff, so I just added the first few terms of (0.6) + (0.6)^2 + (0.6)^3 + ... and saw that it was headed for 1.5 and went from there. Maybe not the way it's supposed to be done, but I bet I could have faked my way to a decent mark on that question.

hahaha, I got that one right and pulled off an 83 on the exam

nice

Originally posted by smomofo
I couldn't remember that stuff, so I just added the first few terms of (0.6) + (0.6)^2 + (0.6)^3 + ... and saw that it was headed for 1.5 and went from there. Maybe not the way it's supposed to be done, but I bet I could have faked my way to a decent mark on that question.

This is a correct approach, you just should show that the series converges.

Find the sum of the first 25 even integers that are larger than 17

930

Originally posted by smomofo
930

lets see, lets see

not what i got but i could be mistaken

😕

Originally posted by Drew L
lets see, lets see

not what i got but i could be mistaken

😕

I got 1050. I did it in groups of 5, 18+20+22+24+26 and found each group starting with 110 sum going up by 50 so it was easy to truncate the series, 110+160+210+260+310= 1050