# What is Pendulum bob: Definition and 21 Discussions

A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing.
From the first scientific investigations of the pendulum around 1602 by Galileo Galilei, the regular motion of pendulums was used for timekeeping, and was the world's most accurate timekeeping technology until the 1930s. The pendulum clock invented by Christiaan Huygens in 1658 became the world's standard timekeeper, used in homes and offices for 270 years, and achieved accuracy of about one second per year before it was superseded as a time standard by the quartz clock in the 1930s. Pendulums are also used in scientific instruments such as accelerometers and seismometers. Historically they were used as gravimeters to measure the acceleration of gravity in geo-physical surveys, and even as a standard of length. The word "pendulum" is new Latin, from the Latin pendulus, meaning 'hanging'.

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1. ### Compound physical pendulum - max velocity

Hi, I'm working on a simple benchmark problem for FEA. It's a pendulum initially positioned at an angle of ##45^{\circ}## and then subjected to gravity. I'm interested in the maximum velocity (when the pendulum is in the vertical position). So far, I've been using this formula: v=\omega \cdot...
2. ### I On whether the motion of a Foucault pendulum bob is comparable to ballistics

A recurring question is: while the motion of a polar Foucault pendulum is fairly straightforward, the case of a non-polar Foucault pendulum is quite difficult to visualize. In 2020, on physics stackexchange someone submitted that question and I contributed an answer. In a comment to another...
3. ### Pendulum hung from the ceiling of a train

(a) No, a person seated inside the train compartment will not be able to tell whether the train is accelerating on a horizontal track or moving uniformly up an inclined track by observing the plumb line. (b) I am assuming that both observers are not allowed to look "out" of the boundaries of...
4. ### Change in the time period of a pendulum

I tried taking log and then diffrentiate the standard equation for time period of a pendulum but i am not getting the correct answer
5. ### Pendulum Hammer Impact Force Calculation

Hi all, I'm a bit embarrassed but I'm extremely rusty with a lot of engineering principles. I've mainly been working in automation and controls within a manufacturing setting and have not done anything like this in ages. Anyways, I have a problem I need to solve and I need to determine the...
6. ### Velocity of the pendulum bob

Homework Statement Show that a simple pendulum bob which has been pulled aside from its equilibrium position through an angle ##\theta## and then released will pass through the equilibrium position with speed ##v = \sqrt{2gl(1-cos\theta)}##, where ##l## is the length of the pendulum. Homework...
7. ### Finding mass of Moon with Pendulum Bob

Homework Statement It is possible to determine the mass of a planet or large moon by using a ‘pendulum bob’ horizontal circular motion experiment. A cosmonaut on the moon finds that a 25 cm long ‘pendulum bob’ moving in uniform horizontal circular motion makes an angle of 22° to the vertical...
8. ### Am I correct in saying the mass of a pendulum bob affects its damping rate

How does the mass of a pendulum bob affect the time taken for the oscillation of a pendulum to diminish? At first I instinctively thought that it would have no effect. However, thinking about the pendulum bob's momentum as it interacts with the air molecules, a higher massed pendulum should...
9. ### The mass of the pendulum bob was determined on an electronic scale and

The mass of the pendulum bob was determined on an electronic scale and its diamter was measured using calipers. The initial height was measured with a meter stick. At the lowest point of its swing, the pendulum bob broke a photogate light beam. The time interval that the light was interrupted...
10. ### Calculating Time of Impact of Pendulum Bob on Cylindrical Bar

Homework Statement A cylindrical metal bar of length L hangs by two strings in a horizontal position. The metal bob of a simple pendulum hits one end of this metal bar in a direction perpendicular to the crossection of the bar. Find an expression for the time t of contact during the impact...
11. ### What is the correct formula for finding tension in a pendulum bob on a string?

A 2 kg pendulum bob on a string that is 3m long is released with a velocity of 1 m/s when the support string makes an angle of 30 degrees with the vertical. What is the tension at the highest point of its motion? The Attempt at a Solution Ok so using Newton's second Law, the equation should...
12. ### Direction of acceleration in pendulum bob?

A simple pendulum consists of a mass M tied to a string and swings freely starting from rest at the position on the left in the figure below. http://imageshack.us/photo/my-images/695/screenshot20110922at611.png/ Select the vectors which best represent the acceleration of mass M at the...
13. ### Optimizing Pendulum Release Height for Maximum Tension and Circular Motion

The pendulum bob in the above figure must circle the rod interrupting its swing, and the string must remain taut at the top of the swing. How far up must the bob be raised before releasing it to accomplish these goals? I don't know where to begin with this because I don't quite understand...
14. ### Deriving a formula for max. speed of a simple pendulum bob

Homework Statement Derive a formula for the maximum speed V_max of a simple pendulum bob in terms of g, the length l and the maximum angle of swing Θ_max. (Hint: Use the fact that the same amount of energy at the top of the arc is the same as at the bottom of the arc.) The picture depicts...
15. ### What is the arc length of a pendulum bob with mass m and length l?

a pendulum bob of mass m hangs on a string of length l. what is the espression for the arc length of the bob if its discplaced through an angle theta.
16. ### What is the maximum speed of the pendulum bob? Need someone to check it.

Homework Statement A grandfather clock is constructed so that it has a simple pendulum that swings from one side to the other, a distance of 23.0 mm, in 1.00 s. A)What is the maximum speed of the pendulum bob? Use two different methods. First, assume SHM and use the relationship between...
17. ### Rotational Motion of a pendulum bob

A pendulum bob is released from some initial height such that the speed of the bob at the bottom of the swing is 3.0 m/s. What is the initial height of the bob? I am not asking to do the problem for me, I am just unsure how to approach this problem. I am just looking for what i need to...
18. ### Angle/distance (Theta) moved by a pendulum bob in t seconds.

Hello. This is not a Physics homework problem, but rather a Programming project. I am asked to model a pendulum using the Java Swing class for graphics, but I'm having a few problems understanding the Physics behind it, and would appreciate a few answers and some guidance. Doing the...
19. ### What is the Speed of a Pendulum Bob?

Homework Statement A simple pendulum consisting of a small heavy bob attached to a light string of length 40cm is released from rest with the string at 60 degrees to the downwards vertical. Find the speed of the pendulum as it passed through its lowest point. Homework Equations Can't find an...
20. ### Calculating Pendulum Bob Properties: Mass 500g, Length 2m, 10° Displacement

1. A mass of 500g is used as a pendulum bob so that it forms a pendulum that is 2meters long. The pendulum is displaced from its rest position by an angle of 10 degrees. A. How high is the pendulum bob above its original position? B. What is the magnitude of the energy that the pendulum bob...
21. ### Bullet and pendulum bob initial speed help momentum.

bullet and pendulum bob...initial speed...help! momentum. Homework Statement An 7.0 g bullet is fired into a 3.5 kg pendulum bob initially at rest and becomes embedded in it. If the pendulum rises a vertical distance of 8.0 cm, calculate the initial speed of the bullet. ________m/s...