Finding net force or acceleration given 2 masses

In summary, the conversation discusses a problem involving a car attached to a pulley with weights. By removing one weight and attaching it to the pulley, the car system remains at a total mass of 900g. The only force acting on the car is the 100g weight and gravity, and the tension in the rope is needed to find the acceleration. Two equations are needed to find the unknowns of tension and acceleration.
  • #1
BSY
9
0

Homework Statement


Imagine you put 10 weights of 100grams on wheels. You attach this "car" to a pulley that hangs over a ledge. You take 1 weight of 100grams off the "car" attach it to the hanging edge of the pulley. The car propels forward what was the acceleration of car and/or net force.

Homework Equations


acceleration=Fnet/mass
 
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  • #2
What's your attempt at a solution?
 
  • #3
I tried using acceleration as the acceleration of gravity to find fnet but the 2 different masses is really throwing me off.
 
  • #4
I forgot to mention that the wheels are "massless" so by removing 1 weight and attaching it to the pulley, the car system is now 900g, and there is 100g on the pulley. No matter what the total mass of the entire system stays the same.
 
  • #5
What is the force acting on the car?
 
  • #6
axmls said:
What is the force acting on the car?
That's what I'm trying to find out. I drew an image of the situation.
 

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  • #7
Don't worry about what's happening anywhere else. Focus only on the car and draw all of the forces acting on the car.
 
  • #8
The only force on the car is the 100g weight + gravity acting on the weight. The car is only moving because of that weight. Is Fapp + Fg in the same direction?
 
  • #9
BSY said:
The only force on the car is the 100g weight + gravity acting on the weight

What exactly do you mean by this?
I see what you're getting at, but you need to be a bit more clear. You're right: there is one force acting on the car. That force is the tension in the rope. Now what is the tension in the rope?
 
  • #10
Okay, I think I'm getting it. I would use the equation g=Fg/m. Since in this situation tension force and gravitation would be the same. It could be written as a=Ft/m. I am unsure what I would put in as mass in that equation, a would be equal to 9.81m/s2, which I am now sure of.
 
  • #11
Actually, I am not sure if it is 9.81, because of the resistance in acceleration the car provides. But I do believe I will use acceleration of gravity in part of the process.
 
  • #12
To find tention force, would I use (0.8kg)(9.81m/s2). Since one mass is on the pulley? Finding what to substitute for mass is my main problem here.
 
  • #13
Let's approach it this way: you've got two unknowns--the tension and the acceleration. That means you'll need two equations to find them. Write out the equations for the net force on each mass.
 
  • #14
Okay. I attached an image of how I think I find Fnet. Only problem with this is that acceleration is always = 9.81m/s2.
 

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FAQ: Finding net force or acceleration given 2 masses

How do I calculate net force given two masses?

To calculate net force, you will need to find the individual forces acting on each mass and then add them together. The formula for net force is Fnet = ma, where m is the mass and a is the acceleration. So, you will need to find the individual forces using the formula F = ma, and then add them together to get the net force.

What is the relationship between force and acceleration?

The relationship between force and acceleration is directly proportional. This means that as the force applied to an object increases, its acceleration also increases. This relationship is described by Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it.

How do I find the individual forces acting on two masses?

To find the individual forces acting on two masses, you will need to use the formula F = ma, where m is the mass and a is the acceleration. You will need to calculate the forces acting on each mass separately, taking into account any external forces such as friction or air resistance. Once you have calculated the individual forces, you can add them together to find the net force.

Can I calculate net force without knowing the mass of the objects?

No, you cannot calculate net force without knowing the mass of the objects. Mass is an essential component in the formula for net force (Fnet = ma). Without knowing the mass, you will not be able to calculate the individual forces or the net force acting on the objects.

How can I use net force to calculate acceleration?

You can use net force to calculate acceleration by rearranging the formula Fnet = ma to a = Fnet/m. This will give you the acceleration of the object in meters per second squared (m/s^2). By calculating the net force and knowing the mass of the object, you can determine the acceleration of the object.

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