Intro Physics projectile problem: Archer fish and grasshopper

In summary, because there is no air resistance, the horizontal velocity is constant. The velocity of the spit is not zero when it hits the bird. This leaves a constant x/horizontal component of velocity, the y vertical component of velocity can be zero at the point which the spit hits the object. Potentially, the y component of velocity could be nonzero at the top, however without any further information given, you can only assume the final y component of velocity is zero at the top.
  • #1
Soccer
4
0
HOMEWORK SUBMITTED IN WRONG FORUM, SO NO TEMPLATE

I uploaded an image of the problem, it seems to be fairly straight forward. However, my textbook indicates the answer as being 6 m/s, I am consistently getting 3 m/s. Any help would be appreciated!

Because there is no air resistance, the horizontal velocity is constant.

2ax+vo^2=vf^2
We can set the Vo equal to zero, find the required speed to achieve .45m vertically.
We find Viy=2.97m/s
vf=at
2.97=at
2.97/9.81=.3 seconds
Horizontal speed (distance over time)- constant speed
.25/.3=.833 m/s
(.833^2+2.97^2)^.5=3m/s

I know that the height and length indicated in the problem yield a angle of 61 degrees, however, this information still does not yield the correct answer.
 

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  • #2
Soccer said:
HOMEWORK SUBMITTED IN WRONG FORUM, SO NO TEMPLATE

I uploaded an image of the problem, it seems to be fairly straight forward. However, my textbook indicates the answer as being 6 m/s, I am consistently getting 3 m/s. Any help would be appreciated!

Because there is no air resistance, the horizontal velocity is constant.

2ax+vo^2=vf^2
We can set the Vo equal to zero, find the required speed to achieve .45m vertically.
On what basis did you set vo equal to zero?
 
  • #3
Chestermiller said:
On what basis did you set vo equal to zero?
You only need to calculate the speed to achieve 0.45m vertically, therefore it would be equivalent to the final speed of an object falling 0.45 meters vertically. Again, no air resistance.
 
  • #4
Soccer said:
You only need to calculate the speed to achieve 0.45m vertically, therefore it would be equivalent to the final speed of an object falling 0.45 meters vertically. Again, no air resistance.
The velocity of the spit is not zero when it hits the bird. So neither the initial velocity nor the final velocity of the spit is zero.
 
  • #5
There remains a constant x/horizontal component of velocity, the y vertical component of velocity can be zero at the point which the spit hits the object. Potentially, the y component of velocity could be nonzero at the top, however without any further information given, you can only assume the final y component of velocity is zero at the top.
 
  • #6
Soccer said:
however without any further information given, you can only assume the final y component of velocity is zero at the top.
No.
You haven't used the given angle of projection in any of your calculations.
 
  • #7
wow, I really appreciate that.. No idea why I decided to overlook the angle, got 6 m/s. Sorry for bothering you guys. Thank you!
 

1. How does the archer fish use physics to catch its prey?

The archer fish uses the principles of projectile motion to catch its prey. It creates a stream of water with a precise amount of force and angle to shoot down its target, just like a projectile launched from a catapult.

2. What factors affect the trajectory of the archer fish's water stream?

The angle of the fish's mouth, the force of the water stream, and the resistance of the surrounding water are the main factors that affect the trajectory of the archer fish's water stream. The fish must also take into account the distance to its target and adjust accordingly.

3. How does the grasshopper's jumping ability play a role in this physics problem?

The grasshopper's jumping ability is a crucial factor in the physics problem. The archer fish must anticipate the grasshopper's jump and adjust the trajectory of its water stream to intercept it. The height, distance, and speed of the grasshopper's jump all affect the timing and accuracy of the archer fish's shot.

4. Is there a specific equation that can be used to solve this problem?

Yes, the equations for projectile motion can be used to solve this problem. These equations take into account the initial velocity, angle of launch, and acceleration due to gravity to determine the trajectory of a projectile. By plugging in the specific values for the archer fish and grasshopper, the scientist can calculate the necessary angle and force for the archer fish's shot.

5. Can this physics problem be applied to other animals or scenarios?

Yes, the principles of projectile motion can be applied to many different scenarios in nature, such as birds catching insects in flight or predators catching prey. These principles also have practical applications in fields such as sports, engineering, and space exploration.

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