Free falling ball with and without air resistance

In summary, the conversation discusses a problem involving a 2 kg ball in free fall with an initial downward velocity of 12 m/s. The goal is to find the difference in displacement after 1s with and without air resistance, using various equations. The displacement without air resistance is calculated to be -16.9m, but the displacement with air resistance cannot be determined without a definition of the "k factor" for air resistance. Additionally, the given units for the k factor (0.02 m-1) are unusual and may not accurately represent air resistance.
  • #1
xcortz
10
0

Homework Statement


A 2 kg ball (k factor of 0.02 m-1) is in free fall. The initial downward velocity of the ball is 12 m/s. Find the difference in displacement after 1s both with and without air resistance.

Homework Equations


vf = vi + at
y = yi + 1/2(vi+vf)t
y - yi = vit + (1/2)At2 - (1/3)Bt3
F = ma

The Attempt at a Solution


I have determined the displacement of the ball without air resistance to be -16.9m by first finding the final velocity after 1s:
vf = vi + at
= -12 + (-9.8)(1s)
= -21.8m/s

And then the final displacement:
y - yi = vit + (1/2)At2 - (1/3)Bt3
= 1/2(-12-21.8)(1s)
= -16.9m

However, I am unable to figure out how to find the displacement of the ball with air resistance present and how to incorporate the k factor. So far, I have determined:
F = (2kg)(-9.8)
= -19.6N

Not sure where to go from here :(
 
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  • #2
They need to define the "k factor" for the air resistance. That is not standard terminology, and it needs to be defined in order to proceed.
 
  • #3
Charles Link said:
They need to define the "k factor" for the air resistance. That is not standard terminology, and it needs to be defined in order to proceed.
It also looks a little suspicious that the units for k are given as ##[m^{-1}]##, since generally air resistance is modeled as being proportional to either ##v## or the square of ##v##.
 
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Likes Yellowkies_3275 and Charles Link
  • #4
gneill said:
It also looks a little suspicious that the units for k are given as ##[m^{-1}]##, since generally air resistance is modeled as being proportional to either ##v## or the square of ##v##.
If we take the units on trust, for factor × something = force the something has to have units of energy. KE maybe? Weird.
 
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Likes Charles Link

1. What is free falling and how does it differ from regular falling?

Free falling is the motion of an object under the sole influence of gravity. It differs from regular falling because it does not encounter any other forces, such as air resistance or friction, that may slow down or change its trajectory.

2. How does air resistance affect the motion of a free falling ball?

Air resistance, also known as drag, is a force that opposes the motion of an object through air. It affects the motion of a free falling ball by slowing it down and changing its trajectory. The larger the surface area of the object, the greater the air resistance will be.

3. What is the equation for calculating the velocity of a free falling ball?

The equation for calculating the velocity of a free falling ball is v = gt, where v is the velocity, g is the acceleration due to gravity (9.8 m/s^2), and t is the time elapsed. This equation assumes no air resistance.

4. How does air resistance impact the acceleration of a free falling ball?

Air resistance acts in the opposite direction of motion, which means it reduces the acceleration of a free falling ball. As the ball falls, the force of gravity and the force of air resistance eventually balance out, resulting in a constant velocity known as terminal velocity.

5. What factors influence the terminal velocity of a free falling ball?

The terminal velocity of a free falling ball is influenced by several factors, including its mass, surface area, and the density and viscosity of the air it is falling through. Objects with larger masses and surface areas will have a higher terminal velocity, while denser and more viscous air will result in a lower terminal velocity.

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