# Homework Help: Throw Up Problem without given velocity or time

1. Oct 1, 2012

### KaylaMarie

"Throw Up" Problem without given velocity or time

1. The problem statement, all variables and given/known data
A stone is thrown straight upward from the edge of a bridge so it passes the bridge on the way down and falls in the river 63.3m below. The stone strikes the water 2.20s after it passes the bridge. Calculate
a) the speed of the stone as it passes the bridge
b)the maximum height above the bridge which the stone attained
(assume there is no air resistance)
2. Relevant equations
There was none given, so I am assuming that its the normal kinematic equations to solve for them such as V=Vo+A*t

3. The attempt at a solution
I literally spent four hours tryinng to solve this problem. I tried manipulating my coordinate system, but nothing seemed to work. However, I do know that the answer for A is 17.99m/s and B is 16.5m

2. Oct 1, 2012

### KaylaMarie

Re: "Throw Up" Problem without given velocity or time

I know those are the answers because my teacher gave us the answers prior to the assignment, just so it might guide us to figure out how to actually solve this impossible problem.

3. Oct 1, 2012

### azizlwl

Re: "Throw Up" Problem without given velocity or time

There are 2 others SUVAT equations and find the one that suit with given data.

4. Oct 1, 2012

### Integral

Staff Emeritus
Re: "Throw Up" Problem without given velocity or time

Treat it as 2 separate problems.

First you need to find the initial velocity of a fall under gravity. You know the distance and time. Should be easy.

Once you have found that, you can use the initial velocity to find the max height. (hint an object returns to the starting point with the same speed it was thrown up with.)

5. Oct 1, 2012

### KaylaMarie

Re: "Throw Up" Problem without given velocity or time

But it was thrown off of a bridge into the water so the starting and ending points are at different levels. Also i wasnt given an initial velocity.

6. Oct 1, 2012

### azizlwl

Re: "Throw Up" Problem without given velocity or time

By conservation of energy, the speed it was thrown up from the bridge, is equal to the speed when it passes down the same level as it plunges down into the water below.

7. Oct 1, 2012

### KaylaMarie

Re: "Throw Up" Problem without given velocity or time

Thanks you guys, got it (: