# Projectile Trajectory

1. Aug 31, 2015

### Beanie

1. The problem statement, all variables and given/known data
A particle travels between two parallel ver- tical walls separated by 25 m. It moves to- ward the opposing wall at a constant rate of 9.2 m/s. It hits the opposite wall at the same height.

The acceleration of gravity is 9.8 m/s2 .

(IMAGE FOR CLARIFICATION ATTACHED)

a) What will be its speed when it hits the opposing wall?
b) At what angle with the wall will the particle strike?

2. Relevant equations
Vf=vi+at
d=vit=.5at^2

3. The attempt at a solution
I've tried this problem (a) many times in many different ways, but continue to get it wrong. I have not yet been able to do problem (b) because of the lack of information (I need to complete a to do b)

Attempts:
The first way I tried was to find the time and then plug it into the second equation described above using d=25, t=2.7, a=-9.8. This resulted in a velocity of 22.52m/s. However this velocity is wrong.

The second way I tried was to find t (same as above) and then use Vx=9.2 as well as t=2.7 to calculate Vy. I found this to be 26.62. I then used the pythagorean theorem using Vx and Vy to find V. My final answer was 28.164m/s. This velocity answer was also wrong.

Any suggestions on where I am going wrong? Are there any other ways of calculating velocity?

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2. Aug 31, 2015

### kuruman

Start by figuring out how the final components of the velocity are related to the initial components when a projectile returns to the same height from which it was launched. Also, it seems that you have found the time of flight. Can you find the initial vertical component of the velocity?

3. Aug 31, 2015

### thecommexokid

Draw a dotted line on your diagram that's exactly halfway between the two walls. Start by focusing only on the part of the particle's trajectory that's between this dotted line and the wall on the right (ignoring for now the other half of the trajectory to the left). Can you use the equations you listed above to determine the vertical speed of the particle at the time it reaches the right wall?