- #1

Dutchli

- 6

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Hello,

I have got an question. How can I calculate the velocity of an object which I'll drop from a height of 1 meters with a starting velocity of 0 m/s?

I did some research myself and found out that I can calculate this with using the following formula:

St = 0.5 * 9.81 * t^2

St = distance

t = time in seconds

So: t^2 = 1 / 0.5 * 9.81 = 0.20 -> t = 0.45 sec

Velocity after 1 meter: v = 9.81 * t -> 9.81 * 0,45 = 4.42 m/s

However, I understand that this is in a vacuum. But I want to know the real velocity in air. Therefore I need to know more about the shape and area of the object and the density of air. Which are:

Shape: half-sphere

Diameter: 2 cm

Mass of the object: 0.2 kg

Area: 0.0006 m^2

Density of air: 1.293 kg*m-3

However, I also found a drag coefficient at: http://en.wikipedia.org/wiki/Drag_coefficient" which is 0.42

I would like to know if I'm right with what I wrote above. How do I calculate the velocity of the object after 1 meters? Can I use the drag coefficient above and how? Or does the coefficient depend too much on the area of the object? Can someone give me an example how I can calculate this?

I have got an question. How can I calculate the velocity of an object which I'll drop from a height of 1 meters with a starting velocity of 0 m/s?

I did some research myself and found out that I can calculate this with using the following formula:

St = 0.5 * 9.81 * t^2

St = distance

t = time in seconds

So: t^2 = 1 / 0.5 * 9.81 = 0.20 -> t = 0.45 sec

Velocity after 1 meter: v = 9.81 * t -> 9.81 * 0,45 = 4.42 m/s

However, I understand that this is in a vacuum. But I want to know the real velocity in air. Therefore I need to know more about the shape and area of the object and the density of air. Which are:

Shape: half-sphere

Diameter: 2 cm

Mass of the object: 0.2 kg

Area: 0.0006 m^2

Density of air: 1.293 kg*m-3

However, I also found a drag coefficient at: http://en.wikipedia.org/wiki/Drag_coefficient" which is 0.42

I would like to know if I'm right with what I wrote above. How do I calculate the velocity of the object after 1 meters? Can I use the drag coefficient above and how? Or does the coefficient depend too much on the area of the object? Can someone give me an example how I can calculate this?

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