Force/magnitude/acceleration scenario

  • Thread starter paperboy221
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In summary: The acceleration if moving up has a greater magnitude. The magnitude of the acceleration if moving down is -G.
  • #1
paperboy221
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Homework Statement


1. Homework Statement
An object is moving vertically while being pulled from above by a rope (or cable, wire, or string). The object is also subject to a significant air resistance force that can't be ignored. All forces acting on it are strictly vertical (pointing up or down only).

Question: If the magnitudes of all forces remain the same, does the object have a greater acceleration if it's rising or if it's descending?

To answer this question, create an appropriate scenario, then draw two FBDs for the object, one for the case in which it's rising, and one for the case in which it's descending. Use N2L and your FBDs to derive expressions that will allow you to calculate the magnitude of the object's acceleration in each case.

Review the summary sheet on FBDs before starting your solution

The only starting equations permitted for this assignment are ΣF = ma and FG =mg

Derive symbolic expressions for the acceleration in each case, then substitute and calculate
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  • #2
This appears to be a duplicate of https://www.physicsforums.com/threads/magnitude-force-acceleration.856945/, which has been marked solved. I assume you did this because the original images were not right.
Forces are vectors. Their magnitudes may be the same but it does not follow that the forces are the same.
You correctly obtained two different expressions for the two accelerations. Try subtracting one from the other.
 
  • #3
haruspex said:
This appears to be a duplicate of https://www.physicsforums.com/threads/magnitude-force-acceleration.856945/, which has been marked solved. I assume you did this because the original images were not right.
Forces are vectors. Their magnitudes may be the same but it does not follow that the forces are the same.
You correctly obtained two different expressions for the two accelerations. Try subtracting one from the other.
I'm having troubling understanding how to put numbers into the equation.
 
  • #4
paperboy221 said:
I'm having troubling understanding how to put numbers into the equation.
You don't need to.
You have two algebraic expressions, one for the acceleration if moving up, one for the acceleration if moving down. You want to find out which acceleration has the greater magnitude.
There are two cases to consider: the accelerations may be in the same direction or in opposite directions.
Pick one of those cases, and write an expression for the difference in the magnitudes.
 

Related to Force/magnitude/acceleration scenario

1. What is force?

Force is a physical quantity that can cause an object to accelerate or change its motion. It can also be defined as a push or pull on an object.

2. How is force measured?

The standard unit of force is the Newton (N). Force can be measured using a spring scale or a force meter.

3. What is magnitude?

Magnitude is a measure of the size or strength of a force. It is typically represented by a number and a unit of measurement, such as 10 N or 5 lbs.

4. How does acceleration relate to force and magnitude?

Acceleration is directly proportional to force and inversely proportional to the mass of an object. This means that the greater the force applied, the greater the acceleration will be. Similarly, a larger magnitude of force will result in a larger magnitude of acceleration.

5. Can an object have a force acting on it without accelerating?

Yes, an object can have a force acting on it without accelerating if the force is balanced by an equal and opposite force. This is known as Newton's First Law of Motion, which states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity, unless acted upon by an unbalanced force.

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