Falling stick with weight on the end

In summary, the problem involves a massless stick with a weight at the end, standing straight up and then being touched slightly causing it to fall over. The weight is 20kg and the length of the stick is 0.5 meters. The equations that can be used to solve this problem are ƩF=\frac{dp}{dt} and Ʃτ=\frac{dL}{dt}. More information is needed to determine if there is any slipping of the end of the stick on the supporting surface. Without this information, it is difficult to solve the problem.
  • #1
leroyjenkens
616
49

Homework Statement



There's a stick with a weight at the end standing straight up and I touch it slightly so it falls over. The stick is massless, the weight is 20kg and the length of the stick is 0.5 meters. How long will it take for the weight at the end to hit the ground?

Homework Equations



[tex]ƩF=\frac{dp}{dt}[/tex]
[tex]Ʃτ=\frac{dL}{dt}[/tex]


The Attempt at a Solution



I don't even know where to begin with this one. This class is horrible. There's no textbook, just examples that aren't similar at all to the problems given on the homework.
 
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  • #2
Hello, leroyjenkens.

Is any information given as to whether or not there is any slipping of the end of the stick that is on the supporting surface?

In accordance with the rules of this forum, you need to show some attempt at a solution before we are allowed to provide any specific help.
 
  • #3
TSny said:
Hello, leroyjenkens.

Is any information given as to whether or not there is any slipping of the end of the stick that is on the supporting surface?

In accordance with the rules of this forum, you need to show some attempt at a solution before we are allowed to provide any specific help.

Thanks for the response.
 
Last edited:
  • #4
Fwiw, if there's no friction it becomes trivial. If there is friction it becomes indeterminate.
 
  • #5


I understand your frustration with the lack of resources and examples in your class. However, let's approach this problem using the equations provided.

First, we need to determine the initial momentum and angular momentum of the system. Since the stick is massless, its initial momentum is zero. The weight at the end has a mass of 20kg and is at a distance of 0.5 meters from the pivot point, so its initial angular momentum is 20kg * 0.5m = 10kg*m/s.

Next, when you touch the stick and it falls, the only external force acting on the system is gravity. This means that the sum of the external forces (ƩF) is equal to just the weight of the end of the stick, which is 20kg * 9.8m/s^2 = 196N.

Using the equation ƩF = dp/dt, we can solve for the time it takes for the weight to hit the ground. Rearranging the equation, we get dt = dp/ƩF. Plugging in the values, we get dt = 10kg*m/s / 196N = 0.051s.

Therefore, it will take approximately 0.051 seconds for the weight at the end of the stick to hit the ground. I hope this helps and that you are able to find additional resources to aid in your understanding of the material.
 

What is the "falling stick with weight on the end" experiment?

The falling stick with weight on the end experiment is a physics experiment that involves dropping a stick with a weight attached to one end and observing its motion as it falls to the ground.

What is the purpose of the "falling stick with weight on the end" experiment?

The purpose of this experiment is to demonstrate the principles of rotational motion and how an object's center of mass affects its motion.

What factors affect the motion of the falling stick with weight on the end?

The motion of the falling stick with weight on the end is affected by the length and mass of the stick, the mass of the weight, and the initial height from which the stick is dropped.

What is the difference between a falling stick with weight on the end and a falling object with a uniform mass distribution?

The main difference between these two scenarios is the point at which the force of gravity acts on the object. In the falling stick experiment, the force of gravity acts at the center of mass of the stick, while in a uniform object, it acts at the center of the object.

How can the "falling stick with weight on the end" experiment be applied in real life?

The principles demonstrated in this experiment can be applied to understand the motion of objects with uneven mass distributions, such as a swinging pendulum or a spinning top. It can also be used to analyze the stability of structures with varying mass distributions, such as a building with a heavier top floor.

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