What is the velocity of the ball after H height? Considering wind resistance?

Click For Summary
SUMMARY

The discussion centers on calculating the velocity of a spherical ball of mass m dropped from a height H into a water tank, considering air and water resistance. Key equations involved include F=ma, Fd = (Cd*p*v^2*A)/2, and Fnet=Fd-Fg. Participants emphasize the need to account for drag force, which is proportional to the square of the velocity, and suggest that calculus is necessary for deriving the velocity equations. The problem remains unresolved, indicating a need for deeper understanding of dynamics and fluid resistance.

PREREQUISITES
  • Understanding of Newton's Second Law (F=ma)
  • Knowledge of drag force equations (Fd = (Cd*p*v^2*A)/2)
  • Familiarity with concepts of net force (Fnet=Fd-Fg)
  • Basic calculus for solving differential equations
NEXT STEPS
  • Study the derivation of velocity equations under the influence of drag forces
  • Learn about the application of calculus in solving motion problems with resistance
  • Explore the concept of terminal velocity in fluid dynamics
  • Investigate numerical methods for simulating motion in resistive mediums
USEFUL FOR

Students in physics, particularly those studying mechanics and fluid dynamics, as well as educators seeking to enhance their teaching of motion under resistance.

TheWhiteKnyt
Messages
2
Reaction score
0
I've been trying to figure out this problem for hours my whole group and most of the class is stumped. We understand that we need to relate the equations of F=ma, Fd = (Cd*p*v^2*A)/2, Fnet=Fd-Fg. No data is given. The answer is a V=____ equation. Even just an answer to #1 would be very helpful! Thanks!

1. Homework Statement


A spherical ball of mass m is dropped from a height H above
the surface of a large water tank. The depth of the water below
is D . The ball hits surface of the water and then continues down
into the water tank, eventually coming to rest at the bottom of the
tank. You should assume that air and water resistance are *not*
negligible in this problem.

1. What is the velocity of the ball when it hits the water?

2. What is the velocity of the ball at the moment it hits the bottom of
the tank?

3. Please draw time-aligned graphs of position, velocity, and acceleration of the ball for its
entire trip from the moment it is dropped until the moment it comes to rest at the bottom of the
tank.

Homework Equations



F=ma, Fd = (Cd*p*v^2*A)/2, Fnet=Fd-Fg.

The Attempt at a Solution



All I've got so far is: Fnet = Fg - Fair = mg - kv(t) = ma(t)
 

Attachments

  • Screen Shot 2014-10-17 at 3.33.35 AM.png
    Screen Shot 2014-10-17 at 3.33.35 AM.png
    23.1 KB · Views: 619
Last edited:
Physics news on Phys.org
TheWhiteKnyt said:
I've been trying to figure out this problem for hours my whole group and most of the class is stumped. We understand that we need to relate the equations of F=ma, Fd = (Cd*p*v^2*A)/2, Fnet=Fd-Fg. No data is given. The answer is a V=____ equation. Even just an answer to #1 would be very helpful! Thanks!

1. Homework Statement


A spherical ball of mass m is dropped from a height H above
the surface of a large water tank. The depth of the water below
is D . The ball hits surface of the water and then continues down
into the water tank, eventually coming to rest at the bottom of the
tank. You should assume that air and water resistance are *not*
negligible in this problem.

1. What is the velocity of the ball when it hits the water?

2. What is the velocity of the ball at the moment it hits the bottom of
the tank?

3. Please draw time-aligned graphs of position, velocity, and acceleration of the ball for its
entire trip from the moment it is dropped until the moment it comes to rest at the bottom of the
tank.

Homework Equations



F=ma, Fd = (Cd*p*v^2*A)/2, Fnet=Fd-Fg.

The Attempt at a Solution



All I've got so far is: Fnet = Fg - Fair = mg - kv(t) = ma(t)

According to the problem statement, the drag force on the ball is proportional to velocity squared, so your equation for Fnet needs correcting.

You won't be able to write your equation for v just by doing algebraic manipulations on the various force quantities. You will have to consult with Mr. Calculus for this problem.
 

Similar threads

  • · Replies 39 ·
2
Replies
39
Views
4K
Replies
7
Views
3K
Replies
34
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 38 ·
2
Replies
38
Views
4K
Replies
7
Views
3K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K