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Rise of an object-Physics (Posted on 2003-04-01) Difficulty: 3 of 5
If a 7kg object is thrown straight upwards at a speed of 10m/s(meters per second)

To what height will it rise? note: gravitational constant = -9.8m/s

See The Solution Submitted by Lucifer    
Rating: 3.2308 (13 votes)

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Solution In vacuum or in air... | Comment 1 of 16
In a vacuum it doesn’t matter what the weight of the object is. At 10 m/s, with gravity accelerating it at 9.8 m/s^2, the object will take 10/9.8 seconds to reach its apex. At an average speed of 5 m/s, it will have traveled 5.102 m up.

In air, at a density of 1.24 kg/m^3, atmospheric resistance, in general, but dependent on shape, would amount to 1.24 A V^2 / 2, where A is the cross sectional area of the object and V is the speed at which it is going, directed opposite to the current motion. When A and V are measured in the MKS system, the force will be in kg-m/s, or Newtons.

If the object is a bowling ball with a diameter of 20 centimeters, being a sphere the air resistance is only about 1/2 that mentioned above, and the ball reaches 5.031 meters at t=1.01 seconds.

If the object has a more irregular shape and is say 1 square meter in cross sectional area, it will get only 2.914 meters up, at t= 0.71 seconds.

These are of course approximate and based on a numerical integration.
  Posted by Charlie on 2003-04-01 09:09:11
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