Solving for Salmon's Speed: vi = ?

[petuniac]

a salmon has to jump a 1.3 m falls to complete its journey. How fast must is be going when it leaves the water to reach the water on top of the falls?

vi = ?
vf = 0 m/s (can i assume this)
a = -9.8 m/s^2
d = 1.3 m
t = ?

use vf^2 = vi^2 + 2ad to find vi

0 = vi^2 + 2(-9.81)(1.3)

but can't take the square root of a negative number?? this is where i am stuck...

 

[OlderDan]

There is no square root of a negative number required. Isolate the vi^2 term

 

[petuniac]

so vi = 5.05 m/s.. is this right?

 

[OlderDan]

so vi = 5.05 m/s.. is this right?

Correct. It is a bit unrealistic though. That would be correct if the salmon could jump vertically to reach the top, which of course is not possible. But it is the correct answer to the question as it was asked.

 

[petuniac]

thanks for your help!