Calculating Air Resistance in Falling Objects

In summary, an object with a mass of 1.21g is falling at a constant velocity of 1.1 m/s. The force of air resistance exerted on the object is about 0.0119N. This is because the acceleration is 0 and the forces of gravity and air resistance cancel each other out, with the force of gravity being about 11.858N. Newtons are measured in (kg*m)/s2.
  • #1
axlg38
12
0

Homework Statement



an object with a mass of 1.21g is falling at a constant velocity of 1.1 m/s. What is the force of air resistance exerted on the object?

Homework Equations



f=ma

The Attempt at a Solution



i imagined that if the object is falling at a constant velocity, then acceleration is 0. so it seems that f=0, but that's obviously not true. i have no idea how to do this

EDIT: according to the book, the answer is about .0119N, I am not sure how to arrive at that answer
 
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  • #2
The acceleration is 0. The velocity is constant. If by "f=0", you mean Ʃf = 0, that is correct.

[Edit: the book is correct]
 
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  • #3
What are the forces acting on the falling body?
 
  • #4
gravity and air resistance?
 
  • #5
Yes! In which direction is gravity working? In which direction is air resistance working?
 
  • #6
gravity is working downward, and air resistance is working upward
 
  • #7
Right, so if acceleration is zero and Ʃf (sum of the forces) = ma = 0, what can you conclude about the magnitudes of the 2 forces?
 
  • #8
They cancel each other out? i thought if that happened, the object wouldn't move at all
 
  • #9
Ah, I see where you are hung up. You should review Newton's 1st law. It is okay for an object to have a constant velocity as long as there is no net force acting on it (think of an object traveling through space, away from significant sources of gravity). In this case, you correctly assert that "they cancel each other out" -- there is no net force acting on the body.

Would you say that the 2 forces are equal and opposite?
 
  • #10
yes?
 
  • #11
Yes! Then we are almost home. What is the force of gravity on the body. Please report in units of Newtons.
 
  • #12
11.858 n
 
  • #13
Almost. [Edit: I'm using "almost" in the broadest sense, meaning you could be off by 3 orders of magnitutde :smile:] Newtons are (kg*m)/s2
 
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  • #14
alright, thanks for the help haha this is going to save me on the test scheduled for tuesday
 

1. What is air resistance?

Air resistance is a type of force that opposes the motion of an object as it moves through the air. It is caused by the collisions of air molecules with the surface of the object, creating a drag force that slows down the object's motion.

2. How does air resistance affect objects?

Air resistance affects objects by slowing them down and reducing their velocity. The larger the surface area of the object, the greater the air resistance it will experience. This force can also cause objects to change direction or even come to a stop if the force is strong enough.

3. What factors affect the force of air resistance?

The force of air resistance is affected by the speed of the object, the density of the air, and the surface area of the object. Higher speeds and denser air will result in a greater force of air resistance, while a larger surface area will also increase the force.

4. How is air resistance measured and calculated?

Air resistance is measured in units of force, such as Newtons (N) or pounds (lbs). It can be calculated using the formula: F = 0.5 * p * v^2 * A * Cd, where F is the force of air resistance, p is the density of air, v is the velocity of the object, A is the surface area, and Cd is the drag coefficient which depends on the shape of the object.

5. How can air resistance be minimized?

Air resistance can be minimized by reducing the surface area of an object, making it more aerodynamic. This can be achieved by shaping the object to have a pointed front and a streamlined body. Lowering the speed and density of the air can also decrease the force of air resistance on an object.

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