Pendulum SHM: Vector Direction of Weight vs. Tension

In summary, the conversation discusses the net restoring force of a pendulum and why the vector direction of the weight is considered instead of the tension. It is explained that the net restoring force is the combination of tension and weight, and its magnitude can be found using trigonometry. Illustrations are also mentioned as a helpful tool to understand the concept.
  • #1
ehabmozart
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0
I've seen in many sites that a pendulum restoring force Fnet = mg sin theta... Why did we actually get the vector direction of the weight and not the vector of the tension.. Simply, as in centrepetal force.. It would be Tsin theta would be the net restoring force? Thanks!
 
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  • #2
The restoring force is the net force acting on the pendulum's bob.
If you add the tension and the weight (as vectors) and consider inextensible suspension string the resultant is tangent to the trajectory and its magnitude is mg sinθ.
 
  • #3
Can i have illustrations then??
 
  • #4
Sure you can. Draw the forces acting on the pendulum and then take the components along the tangential and radial directions.
 
  • #5


I would like to clarify that the direction of the weight and tension in a pendulum's Simple Harmonic Motion (SHM) is determined by the direction of the restoring force. In this case, the restoring force is equal to the weight of the pendulum bob, which is given by the equation Fnet = mg sin theta. This means that the direction of the weight is always towards the center of the Earth, and therefore, the direction of the tension in the pendulum's string or rod will also be towards the center of the Earth.

In contrast, the direction of the tension in a pendulum's string or rod is not always towards the center of the Earth, as in the case of centripetal force. Centripetal force is the net force that keeps an object moving in a circular path, and its direction is always perpendicular to the object's velocity. Therefore, in the case of a pendulum's SHM, the direction of the restoring force (weight) is not perpendicular to the object's velocity, and thus, the direction of the tension cannot be determined using the equation Tsin theta.

In conclusion, the direction of the weight and tension in a pendulum's SHM is determined by the direction of the restoring force, which is always towards the center of the Earth. I hope this clarifies any confusion and helps in understanding the concept of SHM in pendulums.
 

1. What is a pendulum SHM?

A pendulum SHM, or simple harmonic motion, is a type of periodic motion in which an object swings back and forth between two points. It is often described as the motion of a pendulum clock or a swing on a playground.

2. How is the vector direction of weight related to tension in a pendulum SHM?

The weight of a pendulum is the force of gravity acting on the object. It is always directed towards the center of the Earth. The tension in the pendulum's string or rod is the force that keeps the object moving in a circular motion. It is directed towards the center of the circle. In a pendulum SHM, these two forces are constantly changing in magnitude and direction as the object swings back and forth.

3. What factors affect the vector direction of weight and tension in a pendulum SHM?

The vector direction of weight and tension in a pendulum SHM is affected by the length of the pendulum, the mass of the object, and the strength of gravity. A longer pendulum will experience a greater change in tension and weight, while a heavier object will experience a greater change in tension but a smaller change in weight. The strength of gravity also plays a role in determining the magnitude of these forces.

4. How does the vector direction of weight and tension change during a pendulum SHM?

As the pendulum swings back and forth, the vector direction of weight and tension will constantly change. At the highest point of the swing, the weight will be directly downwards and the tension will be directed towards the center of the circle. At the lowest point of the swing, the weight will be directly downwards and the tension will be directed away from the center of the circle.

5. Why is understanding the vector direction of weight and tension important in pendulum SHM?

Understanding the vector direction of weight and tension in a pendulum SHM is important for accurately predicting and analyzing the motion of the pendulum. It also helps in understanding the relationship between different forces acting on the pendulum and how they contribute to the overall motion. This knowledge is essential for many practical applications, such as in the design of pendulum clocks and other mechanical systems.

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