Calculate terminal velocity when given cross sectional area

In summary, the conversation is about two packages being dropped from an airplane with different parachutes. The parachute on package 1 fails to open, and the terminal speed is 10 m/s. The parachute on package 2 opens, and the question asks for the terminal speed of package 2 in m/s. The attempted solution involves using the equation R = ½CρAv2 and solving for the final step. After receiving a hint, the person realizes their mistake and correctly calculates the terminal speed of package 2.
  • #1
Tatortotts
4
0

Homework Statement


Two packages are dropped from an airplane. A parachute can increase the cross sectional area of each packages by a factor of 31. The parachute on package 1 fails to open, and the terminal speed of package 1 is 10 m/s. The parachute on package 2 opens.

What is the terminal speed of package 2 in m/s?

Homework Equations


Unsure, considering the problem gave very few numbers to work with.
R = ½CρAv2

The Attempt at a Solution


I figured since A (cross sectional area) is inversely proportional to vterminal2, that you would square package 1's vterminal (to get 100 m/s) and then divide by 31. I haven't submitted my answer yet so I'm not sure if it's right.
 
Physics news on Phys.org
  • #2
Tatortotts said:
I figured since A (cross sectional area) is inversely proportional to vterminal2, that you would square package 1's vterminal (to get 100 m/s) and then divide by 31.
Have you left out a final step?
 
  • #3
haruspex said:
Have you left out a final step?
Well, vterminal2 is proportional to 1/A, so 102 = 1/(A*31)
Solving for A I then get 1/3100 m/s, which seems a little ridiculous.
I submitted my answer (from my original solution--3.2 m/s) and it was wrong, so I know I'm missing something. I just can't seem to figure out what.
 
  • #4
Tatortotts said:
Well, vterminal2 is proportional to 1/A, so 102 = 1/(A*31)
Solving for A I then get 1/3100 m/s, which seems a little ridiculous.
I submitted my answer (from my original solution--3.2 m/s) and it was wrong, so I know I'm missing something. I just can't seem to figure out what.
Here's a hint. The square of 10m/s is not 100m/s. What is it?
 
  • #5
haruspex said:
Here's a hint. The square of 10m/s is not 100m/s. What is it?
Would it then be 100m2/s2? So I should take the square root of my answer?
 
  • #6
Tatortotts said:
Would it then be 100m2/s2? So I should take the square root of my answer?
Yes.
 
  • Like
Likes Tatortotts
  • #7
haruspex said:
Yes.
Thank you so much! I don't know why I decided to neglect units for that problem.
 

Related to Calculate terminal velocity when given cross sectional area

1. How is terminal velocity calculated?

Terminal velocity is calculated using the formula: Vt = √(2mg/ρAC), where Vt is the terminal velocity, m is the mass of the object, g is the acceleration due to gravity, ρ is the density of the fluid, A is the cross sectional area of the object, and C is the drag coefficient.

2. What is the significance of the cross sectional area in calculating terminal velocity?

The cross sectional area of an object is an important factor in calculating terminal velocity because it affects the amount of air resistance or drag that the object experiences. The larger the cross sectional area, the more air resistance the object will experience, resulting in a lower terminal velocity.

3. Can terminal velocity be different for objects with the same cross sectional area?

Yes, terminal velocity can be different for objects with the same cross sectional area. This is because the terminal velocity also depends on the mass, density, and drag coefficient of the object. Objects with the same cross sectional area but different masses, densities, or drag coefficients will have different terminal velocities.

4. How does air density affect terminal velocity?

Air density plays a significant role in determining the terminal velocity of an object. Objects falling through less dense air will experience less air resistance, resulting in a higher terminal velocity. Similarly, objects falling through denser air will experience more air resistance, resulting in a lower terminal velocity.

5. Is the drag coefficient the same for all objects?

No, the drag coefficient can vary depending on the shape and size of the object. Objects with a streamlined shape will have a lower drag coefficient compared to objects with a less streamlined shape. Additionally, the surface roughness of an object can also affect the drag coefficient.

Similar threads

  • Introductory Physics Homework Help
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
13
Views
3K
  • Introductory Physics Homework Help
2
Replies
57
Views
717
  • Introductory Physics Homework Help
Replies
2
Views
10K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
7K
  • Introductory Physics Homework Help
Replies
9
Views
4K
Replies
6
Views
3K
  • Introductory Physics Homework Help
Replies
4
Views
2K
Back
Top