How fast must Romeo throw pebbles to hit Juliet's window with minimum speed?

[SnowOwl18]

I posted this the other day, but I only got one response from someone that was a reminder that the pebble would be following a parabolic path...but what need help with is going about solving the problem...here's the problem and what I tried again..sorry to post the same problem again, but I thought maybe with all the posts no one saw it. Any help would be awesome )

*Romeo is chucking pebbles as gently as he can up to Juliet's window. That is, he wants the pebbles to hit the window with the least possible speed...He is standing at the edge of a rose garden at H = 7.70m below her window and at D = 8.90m from the base of the wall. How fast are the pebbles going when they hit her window?*

Ok, so the horizontal component is 8.9m and the vertical is 7.7m...I tried
- tan= 7.7/8.9 to get theta and then use that to get the hypoteneuse, but i realized, after getting the problem wrong, that I only got the distance of the hypoteneuse, when i really needed the velocity...so how would i find that? thanks for any help

 

[Pyrrhus]

Draw a picture, and review projectile motion.

 

[Sirus]

Yes, that person who told you about the parabolic path was me. I also tried to get you to identify the point at which the speed would be the smallest, which is the summit of its trajectory (because at that point the pebble has no vertical speed). You have the vertical distance, the final vertical velocity, and the acceleration due to gravity, so can you find how long it takes to reach Juliet's window? From there you should be able to find the final answer.

 

[DarkEternal]

do you go to MIT?

 

[Sirus]

No, umm...why?

 

[DarkEternal]

no, the original poster. this was on the problem set for the freshmen and i noticed the original poster was from massachusetts.

 

[Sirus]

Surprising. This seems a little too basic for MIT standards.

 

[SnowOwl18]

k thanks, I will try that ) Nope, I go to the University of Michigan at Ann Arbor...the questions are easy because it's an algebra based physics class

 

[DarkEternal]

yeah, it is. well, it is the first pset, and it is for 8.01. 8.012, the more advanced version, uses kleppner amd kolenkow. i think this is from giancoli or somethin similar.