# Tension in a Pendulum String - Oh my

• Engineering101
In summary: The tension in the string is equal to the weight of the mass times the sine of the angle, in this case it is equal to 0.27 N.In summary, the conversation discusses finding the tension in a pendulum with a 0.030 kg mass and a 0.42 m long string when it is released at an angle of 25°. One solution is T = 0.32 N, while another suggests T = 0.27 N. The discussion also mentions that the centripetal force is zero at the extreme position, but this does not mean that T = 0. The final conclusion is that T = 0.27 N is correct.

#### Engineering101

So I have one attempt left and want to make sure my answer is correct, so double checking me would be super awesome!

You are given a pendulum composed of a 0.030 kg mass on the end of a 0.42 m long massless string. The pendulum is moved 25° from the vertical and released. Find the tension in the string when the mass is at the release point,
θ = 25°.

Tsin(65)-mg=0
Tsin(65)=mg
T=.32 N

This is one solution I came up with.

The other option I am unsure of is if the T force would be 0 because "there is no net force directed along the axis that is perpendicular to the motion. Since the motion of the object is momentarily paused, there is no need for a centripetal force." -http://www.physicsclassroom.com/class/waves/u10l0c.cfm

Thanks for the guidance.

The centripetal force is indeed zero in the extreme position. However this does not imply T=0.
The net force along the radial direction should be zero. And this net force includes gravity's contribution as well.

The first "option" is not good because the body's acceleration along the vertical direction is not zero.

• harmyder
So,
T=mgsin(65)
T=.27 N

So I have one attempt left and want to make sure my answer is correct, so double checking me would be super awesome!

You are given a pendulum composed of a 0.030 kg mass on the end of a 0.42 m long massless string. The pendulum is moved 25° from the vertical and released. Find the tension in the string when the mass is at the release point,
θ = 25°.

"The centripetal force is indeed zero in the extreme position. However this does not imply T=0.
The net force along the radial direction should be zero. And this net force includes gravity's contribution as well."--nasu

So,
T=mgsin(65)
T=.27 N

Engineering101 said:
So I have one attempt left and want to make sure my answer is correct, so double checking me would be super awesome!

You are given a pendulum composed of a 0.030 kg mass on the end of a 0.42 m long massless string. The pendulum is moved 25° from the vertical and released. Find the tension in the string when the mass is at the release point,
θ = 25°.

"The centripetal force is indeed zero in the extreme position. However this does not imply T=0.
The net force along the radial direction should be zero. And this net force includes gravity's contribution as well."--nasu

So,
T=mgsin(65)
T=.27 N

It is correct.

ehild

## 1. What is a pendulum string?

A pendulum string is a string or wire used to suspend a pendulum from a fixed point. It allows the pendulum to swing freely back and forth in a regular motion.

## 2. How does tension affect a pendulum string?

Tension is the force that pulls the pendulum string taut. The higher the tension, the faster the pendulum will swing. If there is not enough tension, the pendulum may not swing at all.

## 3. What factors can affect the tension in a pendulum string?

The length of the pendulum, the weight of the pendulum, and the angle at which the pendulum is released can all affect the tension in a pendulum string. Other factors such as air resistance and gravity may also play a role.

## 4. How can you measure the tension in a pendulum string?

The tension in a pendulum string can be measured using a spring scale or a force meter. Simply attach the scale to the string and pull it downwards to measure the force exerted by the string.

## 5. How does tension impact the motion of a pendulum?

Tension is a crucial factor in determining the motion of a pendulum. Without enough tension, the pendulum may not swing at all. The higher the tension, the faster the pendulum will swing, and the shorter the period of the pendulum's motion will be.