Calculating Pull Force on Weights Connected by Cords

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In summary, the conversation discusses a series of weights connected by cords and given an upward acceleration by a pull. The tensions in the connecting cords are denoted as A, B, and C. The question asks for the value of the pull, which is closest to one of the given options. The attempted solution involves treating the weights as one mass and using the equation F=ma, but the final calculation is incorrect due to an error in adding the masses.
  • #1
Motorboar
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Homework Statement


A series of weights connected by very light cords are given an upward acceleration of 4.00 m/s2 by a pull P, as shown in Fig. 5.3.( a verticle strand of 4 balls with mass 5,10,15,and 20 kg with the pull at the top) A, B, and C are the tensions in the connecting cords.
the pull P is closest to:

290 N
690 N
50 N
200 N
490 N

Homework Equations


F= ma


The Attempt at a Solution


treating the weights as one mass
Pull-mg=ma
pull=m(a+g)
= 552
Which is not one of the answers. What is the error in my logic?
 
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  • #2
Motorboar said:

The Attempt at a Solution


treating the weights as one mass
Pull-mg=ma
pull=m(a+g)
= 552
Which is not one of the answers. What is the error in my logic?

I'm don't see an error in your logic (if I'm interpreting your description of the figure correctly). :approve: Maybe there's an error in your calculations? :uhh: What did you use for m and g?

[Edit: In other words, your equations seem fine. But I don't know why you ended up with 552]
 
  • #3
added the masses wrong xD Thank you.
 

1. What is the formula for calculating force in a weight problem?

The formula for calculating force in a weight problem is F = m x a, where F represents force, m represents mass, and a represents acceleration.

2. How do I determine the weight of an object given its mass and acceleration?

To determine the weight of an object, multiply its mass by the acceleration due to gravity, which is typically 9.8 m/s².

3. What is the difference between weight and mass in a force problem?

Weight is a measure of the force of gravity on an object, while mass is a measure of the amount of matter in an object. In a force problem, weight is calculated using the formula F = m x a, while mass is typically given in the problem.

4. How do I calculate the net force in a weight problem?

To calculate the net force, add together all the individual forces acting on an object. In a weight problem, this may include the force of gravity and any other forces that are present, such as friction or applied forces.

5. What is the unit of measurement for force in a weight problem?

The unit of measurement for force in a weight problem is typically Newtons (N). However, other units such as pounds (lb) or kilograms (kg) may also be used, depending on the problem.

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