# Homework Help: A rock is thrown at an angle of 17 degrees above the horizontal at 28.5 m/s, from the

1. Feb 7, 2009

### liz777

1. The problem statement, all variables and given/known data

A rock is thrown at an angle of 17 degrees above the horizontal at 28.5 m/s, from the ground.

a)How high will the rock rise above the ground?
b)What is the horizontal speed of the rock at the top of its flight?
c) How long will it take the rock to reach a vertical speed of zero m/s?

3. The attempt at a solution
First I found out what the x and y components are. x=27.25 m/s and y=8.35 m/s. Then I found the time w/ vf=vi+at. (27.25=9.8t)

a)I used the forumla d=vit+1/2at^2 and it came out to 37.87 m
=1/2(9.8)(2.78)^2
b) I'm guessing I would use the formula v=d/t. So the max height is 37.87 and the time is 2.78(1/2 the time of the rock's total air time). and I got the answer 13.62 m/s
c) I wasnt really sure on this one. Is it 2.78s, when the ball is at the top of its flight?

Any advice/help would be great. I want to make sure I'm doing this correctly. Thanks! :)

2. Feb 7, 2009

### casedogg

Re: A rock is thrown at an angle of 17 degrees above the horizontal at 28.5 m/s, from

The horizontal velocity never changes

3. Feb 7, 2009

### Trentonx

Re: A rock is thrown at an angle of 17 degrees above the horizontal at 28.5 m/s, from