Time for a Droplet of Water to Fall .25m from Hole

Click For Summary
The discussion focuses on calculating the time it takes for a droplet of water to fall 0.25 meters from a hole in a cylindrical tank. The user attempted to solve the problem using the kinematic equation but encountered issues with the quadratic formula, resulting in a negative answer. The correct time for the droplet to fall is 0.062 seconds, which differs from the user's initial calculations. Another participant suggests that the method is correct, but the application of the quadratic formula may have been flawed. The conversation emphasizes the importance of accurately applying mathematical principles to achieve the correct results.
skoopfadj
Messages
8
Reaction score
0
Time for Droplet of Water to Fall .25m from Hole

Homework Statement



A cylindrical tank .7m tall is filled with water and placed on a stand (below it) that is .3m tall. A hole of radius .001 m in the bottom of tank is opened. Water then flows through the hole and through an opening in the stand and is collected in a tray .3 m below the hole. At the same time, water is added to the tank at an appropriate rate so that the water level in the tank remains constant.
Find:
^The speed at which the water flows out from the hole
[Done: 3.7 m/s]
^The volume rate at which water flows out from the hole
[Done: 1.1623893 x 10-5 m3/s]
^The volume of water collected in the tray in 2 minutes
[Done: .0013948672 m3]
^ ! The time it takes for a droplet of water to fall 0 .25 m from the hole.

Homework Equations



Density of Water: 1000 kg/m3

3. The attempt

- PART D -

*The time it takes for a droplet of water to fall 0 .25 m from the hole.
ΔX = V°*t + (1/2)*a*t2
-
.25 = 3.7t + (1/2)(9.8)t2
-
4.9t2 + 3.7t - 0.25 = 0
- Used Quadratic Equation but answer turned out negative and does not match answers -
? ? ?
Correct Answer: 0. 062 seconds
My question is how.
 
Last edited:
Physics news on Phys.org


skoopfadj said:
4.9t2 + 3.7t - 0.25 = 0
- Used Quadratic Equation but answer turned out negative and does not match answers -
? ? ?
Correct Answer: 0. 062 seconds
My question is how.
Show your quadratic formula workings. Something must've gone awry, because I get two results and one of them matches the expected value.
 
I pretty much laid out the whole schema. I know the quadratic equation I provided gives answers that do not match the correct one (as I stated earlier). However, I'm not sure if I'm even supposed to use the kinematics equation listed above in order to solve the problem.
The answer may even be 0.021 seconds but my professor informed me that 0.021 was not the answer and promptly replaced the old answer with 0.062 seconds.
 
skoopfadj said:
I pretty much laid out the whole schema. I know the quadratic equation gives answers that do not match the correct one (as I stated earlier). However, I'm not sure if I'm even supposed to use the kinematics equation listed above in order to solve the problem.

The method is fine. What I'm saying is, something went wrong in your application of the quadratic formula. as I obtained the correct result using the same starting point.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
9K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
16
Views
2K
  • · Replies 21 ·
Replies
21
Views
9K
  • · Replies 47 ·
2
Replies
47
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K