Coursework Experiment involving rotational mechanics

[Zoe-b]

The experiment for my A level coursework is as follows:
Place a pencil so that it is balancing with one end hanging off a table (and is perpendicular to the table edge). Apply a force (eg by hitting it with the side of the hand) to the end hanging off, so that the pencil flies across the room. (It makes sense once you try it!)

I am not looking for specific equations (although if you can think of any directly relevant I would be grateful), more some other thoughts on how this might work. I have carried out various experiments- my set-up involves placing the pencil so that a recorded distance hangs off the table, and then dropping a mass through a tube onto the end of the pencil. I have tried changing the mass and also the distance the pencil hangs off and got some very interesting (but not so conclusive!) results.

I am getting a variation of approximately 80cm between my results for each mass (eg a 20g mass can produce any distance from 1.6m to 2.4m)- this may just be down to the inaccuracy of my experimental set-up, as I think the mass may hit the pencil in a very slightly different place each time.

Thinking about the mechanics of the situation- the centre of mass of the pencil should travel with parabolic motion, although I'm not sure how to work out the angle the pencil sets off at as the rotation makes this hard to find. I should be able to measure it from the videos I have made.

One thing that is currently baffling me (and my teachers!) is that; when the pencil is placed so only a small length hangs off the end of the table (eg 3-4cm), the pencil sometimes jumps upwards and backwards (towards the centre of the table) instead of the usual forwards motion. (This does not seem to happen EVERY time- I have video shots if you don't believe me!) I have no idea how this could happen as I cannot find any backwards component to the forces I am considering.

I realize this is an extremely long post so thank you for reading it! I have more information on the situation if needed. Thanks in advance for any replies.

 

[anathema]

Thank you for sharing your A level coursework experiment with us. It sounds like you have put a lot of thought and effort into your set-up and data collection. From what you have described, it seems like you are on the right track in terms of understanding the mechanics of the situation.

One factor that could be contributing to the variation in your results is the accuracy of your experimental set-up. As you mentioned, the mass hitting the pencil in a slightly different place each time could affect the distance it travels. It may be helpful to try and minimize this variation by ensuring that the mass is hitting the pencil in the same spot each time.

Regarding the angle at which the pencil sets off, you could try using a video analysis software to track the motion of the pencil and determine the angle. Alternatively, you could also measure the angle using trigonometry and the known distances and heights involved in the experiment.

The phenomenon of the pencil sometimes jumping upwards and backwards is quite interesting. It could be due to the rotation of the pencil as it is hit, causing it to have a slight upwards and backwards motion before it starts moving forwards. Another factor could be the friction between the pencil and the table, which could cause it to jump in a different direction depending on the surface of the table.

Overall, I think you are on the right track with your experiment and data analysis. It may be helpful to continue exploring different factors that could affect the results, such as the surface of the table and the angle at which the pencil is hit. Good luck with your coursework!

 

[ogb p]

I find this experiment on rotational mechanics to be quite interesting. It seems like you have put a lot of effort into setting up and conducting the experiment, which is commendable. From your description, it appears that you are trying to understand the motion of a pencil when it is hit with a force on one end while balancing on the other end.

Firstly, it is important to consider the various forces acting on the pencil during the experiment. The force applied by hitting the pencil causes a torque, which results in the pencil rotating around its center of mass. At the same time, the weight of the pencil and the force of gravity also play a role in its motion. Additionally, air resistance and friction may also affect the motion of the pencil.

Your results showing a variation in the distance traveled by the pencil for each mass can be attributed to these factors. As you mentioned, the inaccuracy of your experimental setup and the slight variations in the position of the pencil when hit may also contribute to this variation.

In terms of the angle at which the pencil sets off, it can be calculated using the principles of rotational dynamics. The angular velocity of the pencil can also be determined from the videos you have recorded.

The phenomenon of the pencil sometimes jumping upwards and backwards is indeed puzzling. It could be due to a combination of factors such as the force applied, the position of the pencil, and the surface it is placed on. Further experimentation and analysis may be needed to understand this behavior.

Overall, your experiment is a great way to explore rotational mechanics and its applications. I suggest continuing to gather more data and analyzing it to draw meaningful conclusions. Best of luck with your coursework!