Another Double Check FBD String Tension

In summary: But for Fg and m, they are different for each mass, so it would be better to use different variable names (ex: Fg1 and m1 for mass 1, and Fg2 and m2 for mass 2) to avoid confusion.
  • #1
Inferior Mind
14
0
Calculate the tension in the cable connecting the two masses. Assume all surfaces are frictionless.

FBD
Physics Question 4 U1-C.gif


m1 = 5 kg
θ1 = 60°
m2 = 6 kg
θ2 = 70°

Equation 1 ~

FT - Fg = ma

FT - mgSinθ = ma

FT = 5a + 5(9.8)Sin60

FT = 5a + 42.44

Equation 2 ~

Fg - FT = ma

mgSinθ - FT = ma

6(9.8)Sin70 - 6a = FT

FT = 55.25 - 6a

~Set Equations Equal to Each Other ~

5a + 42.44 = 55.25 - 6a

11a = 12.81

a = 1.16 m/s2

~Sub into Eq to find Force Tension on da String Son !~

5(1.16) + 5(9.8)Sin60 = FT

FT = 48.2 N
 
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  • #2
Inferior Mind said:
Calculate the tension in the cable connecting the two masses. Assume all surfaces are frictionless.

FBD
View attachment 55356

m1 = 5 kg
θ1 = 60°
m2 = 6 kg
θ2 = 70°

Equation 1 ~

FT - Fg = ma

FT - mgSinθ = ma

FT = 5a + 5(9.8)Sin60

FT = 5a + 42.44

Equation 2 ~

Fg - FT = ma

mgSinθ - FT = ma

6(9.8)Sin70 - 6a = FT

FT = 55.25 - 6a

~Set Equations Equal to Each Other ~

5a + 42.44 = 55.25 - 6a

11a = 12.81

a = 1.16 m/s2

~Sub into Eq to find Force Tension on da String Son !~

5(1.16) + 5(9.8)Sin60 = FT

FT = 48.2 N
The results looks correct.

Comment: If I were grading this, I would be concerned that you are using the same variable names for mass 1 quantities and mass 2 quantities, particularly Fg and m .
 
  • #3
SammyS said:
The results looks correct.

Comment: If I were grading this, I would be concerned that you are using the same variable names for mass 1 quantities and mass 2 quantities, particularly Fg and m .

Thanks for the input, I will make amends in future questions.
 
  • #4
Inferior Mind said:
Thanks for the input, I will make amends in future questions.
To be more specific: FT and a are the same in magnitude for both masses, so it's fine to use the same variable name for them.
 
Last edited:
  • #5


Based on the given information and equations, the tension in the cable connecting the two masses is 48.2 Newtons. This calculation assumes that all surfaces are frictionless and that the only forces acting on the masses are gravity and the tension in the cable. It is important to double check calculations like this to ensure accuracy and to account for any possible errors. Further experimentation or analysis may be necessary to confirm the calculated tension value.
 

1. What is a FBD (Free Body Diagram) and why is it important in physics?

A FBD is a simplified diagram that represents the forces acting on an object. It is important in physics because it helps to visualize and analyze the different forces that are acting on an object, making it easier to understand the motion and behavior of the object.

2. How is string tension related to FBDs?

In an FBD, string tension is represented as a force acting on an object. This force is typically represented by an arrow pointing away from the object and labeled with the magnitude of the tension. String tension is an important factor in FBDs, especially in situations involving objects connected by strings or ropes.

3. How do you calculate string tension in an FBD?

In order to calculate string tension in an FBD, you must first identify all the forces acting on the object connected to the string. Then, you can use Newton's second law (F=ma) to calculate the net force acting on the object. The tension in the string can be calculated by finding the difference between the net force and the other forces acting on the object.

4. Can string tension change in an FBD?

Yes, string tension can change in an FBD. This can happen if the magnitude or direction of the net force acting on the object changes. For example, if an object is moving in a circular motion, the tension in the string will constantly change as the direction of the net force changes.

5. How can understanding FBDs and string tension help in real-world situations?

Understanding FBDs and string tension can help in various real-world situations, such as designing structures, analyzing the motion of objects, and predicting the behavior of systems. For example, engineers use FBDs and string tension calculations to design bridges and buildings that can withstand different forces and loads. Understanding these concepts can also help in sports, such as understanding the trajectory of a ball in flight or the forces acting on a gymnast during a routine.

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