# Can't for the life of me figure out the two parts of this question. 1-d kinematics

1. Sep 7, 2011

### magellaniic

A blue ball is thrown upward with an initial speed of 23.5 m/s, from a height of 0.9 meters above the ground. 2.9 seconds after the blue ball is thrown, a red ball is thrown down with an initial speed of 11.9 m/s from a height of 31.4 meters above the ground. The force of gravity due to the earth results in the balls each having a constant downward acceleration of 9.81 m/s^2.

The Two questions are the following:

What is the height of the red ball 3.77 seconds after the blue ball is thrown?

and

How long after the blue ball is thrown are the two balls in the air at the same height?

Thanks for help much appreciated.

2. Sep 7, 2011

### Spinnor

Re: Can't for the life of me figure out the two parts of this question. 1-d kinematic

Can you set up the equation to describe the blue ball?

Then set up a similar equation for the red ball but you will have to shift the time coordinate for the red ball by 2.9 seconds. From there it should be easy.

3. Sep 7, 2011

### magellaniic

Re: Can't for the life of me figure out the two parts of this question. 1-d kinematic

Got it thanks :)