How Does the Archerfish Use Projectile Motion to Hunt?

[wolves5]

The archerfish hunts by dislodging an unsuspecting insect from its resting place with a stream of water expelled from the fish's mouth. Suppose the archerfish squirts water with an initial speed of 2.36 m/sec at an angle of 20.7 degrees above the horizontal. When the stream reachs the beetle a height h avoe the water's surface it is moving horizontal.

https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/Phys1201/fall-evening/homework/Ch-04-2D-Motion/wt-archer-fish/archer-fish.gif

(a) What is the vertical component of the water's initial velocity?

I got 0.83 for part a. I did 2.36cos(20.7)

(b) How long does the bettle have to react?

I don't know what to do for this one.

(c) How high is the bettle above the fish?

Would you use d= (vi +vf)/2 x t. You would use the time found in part b right?

(d) What is the horizontal distance between the fish and the bettle?

I'm confused about this one too.

 

[ehild]

Very nice picture, indeed!

(a) What is the vertical component of the water's initial velocity?

I got 0.83 for part a. I did 2.36cos(20.7)

You calculated with sine instead of cosine, I am afraid.

(b) How long does the bettle have to react?

I don't know what to do for this one.

Read the problem, the water stream is horizontal when it reaches the beetle. What is the vertical component of velocity there?
How do you get the vertical component of velocity in terms of time?

(c) How high is the bettle above the fish?

Would you use d= (vi +vf)/2 x t. You would use the time found in part b right?

What are vi and vf? Take care, this is a two-dimensional motion, you need to treat the horizontal and vertical components separated. And yes, you can use the time you got in part b.

(d) What is the horizontal distance between the fish and the bettle?

I'm confused about this one too.

This is projectile motion and it can be decomposed into a vertical motion and a horizontal one. What is the velocity of the horizontal motion?

ehild