Calculating tension of moving object

  • Thread starter Cleo>_>
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In summary, the conversation discusses the calculation of tension in a system with two masses, M1 and M2, attached to a cable hung over a pulley. The net force and net moment are given as 20N and 8N, respectively, and the system is accelerating at 2.5ms-2. The tension in the cable is determined to be the same at both ends, but in opposite directions according to Newton's 3rd law. The importance of drawing free body diagrams is emphasized for understanding and solving such problems.
  • #1
Cleo>_>
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So two masses M1 and M2, are attached to each end of a cable, and the cable was hung over a pulley.

M1 is 5kg
M2 is 3kg

ΣF=20N
ΣM=8N

The system would be accelerating at 2.5ms-2 but how would you calculate the tension of the cable?

(g=10, cable is massless, pulley is frictionless)
 
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  • #2
I would guess it is 5*10 + 3*10 = 80N but the system is accelerating
 
  • #3
Draw a free body diagram for one of the masses. You know how fast the mass is accelerating so you know the the net force.
 
  • #4
okay I did not realize tension on both ends can be different, but the question asks for the tension of the cable, would it be the total force acting on the calbe from both ends?
 
  • #5
The tension would be different only if there is friction in the pulley.
For this problem you should assume then that its the same at both ends.
No the tension in the cable is in opposite directions at the two ends so the total
tension would then be zero! That is why it is called tension in the cable it pulls
in opposite directions at the two ends and keeps it under tension. The tension
in the cable, Tc, and the force it exerts on a masspiece, Tm,
is the same, but they are in opposite directions, that is they form an action-reaction
pair according to Newton's 3rd law.
 
  • #6
The reason that you are having so much trouble with this problem is that you have not drawn free body diagrams of the two masses. Do you feel that you have advanced to the point where you no longer need to use free body diagrams? This problem kind of shows that you haven't.

Chet
 
  • #7
It seems i have misunderstood tension, thanks for the help, I'll remember to draw free body diagrams next times
 

Related to Calculating tension of moving object

What is tension?

Tension is a force that is exerted on an object when it is being pulled or stretched. It is measured in units of newtons (N).

How do you calculate tension?

To calculate tension, you need to know the mass of the object (m) and its acceleration (a). The formula for tension is T = ma, where T is the tension in newtons.

What is the difference between static and dynamic tension?

Static tension is the force applied to a stationary object, while dynamic tension is the force applied to a moving object. The formula for calculating tension in a static situation is the same as the formula for calculating weight, which is T = mg, where g is the acceleration due to gravity.

How does friction affect tension?

Friction can affect the tension on an object by either increasing or decreasing it. If there is less friction, there will be less resistance to the movement of the object, resulting in a lower tension. Conversely, if there is more friction, there will be more resistance, resulting in a higher tension.

What is the relationship between tension and velocity?

Tension and velocity are indirectly related. As the velocity of an object increases, the tension on it will also increase. This is because a higher velocity means a higher acceleration, which in turn means a higher tension according to the formula T = ma.

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