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

Click For Summary

Homework Help Overview

The problem involves a cylindrical tank filled with water, where a droplet of water falls from a hole at the bottom of the tank to a tray below. The specific focus is on calculating the time it takes for the droplet to fall a distance of 0.25 meters, given the speed of water flowing out from the hole and the acceleration due to gravity.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of the kinematic equation to determine the time of fall, with one participant expressing uncertainty about whether this equation is appropriate for the problem.
  • There is mention of using the quadratic formula to solve for time, but discrepancies in the results lead to questions about the application of the formula.
  • Some participants question the validity of the derived answers and the assumptions made in the calculations.

Discussion Status

The discussion is ongoing, with participants sharing their attempts to apply the quadratic formula and expressing confusion over the results. There is a recognition that one participant has arrived at the expected answer, while others are still trying to reconcile their calculations with the correct value.

Contextual Notes

Participants note that the professor has indicated a specific correct answer, which adds pressure to verify the calculations. There is also mention of potential errors in applying the kinematic equation and the quadratic formula, highlighting the need for careful consideration of the problem setup.

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.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
10K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
16
Views
2K
  • · Replies 21 ·
Replies
21
Views
9K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 47 ·
2
Replies
47
Views
5K