Galileo Galilei came up with the famous falling objects experiment to prove that objects accelerate at the same rate. All falling objects do accelerate at the same rate in a vacuum; however, in the presence of air resistance the condition will change. Our experiment considers how air resistance has an impact on the velocities of different objects. After our team finished designing the experiment, we went to present it at Dorchester Academy and Tech Boston for high school students. The blog will discuss the theory, procedure and the result of our experiment, in addition to the students’ reactions.
Theory:
The hypothesis of this experiment depend on how we visualize things around us. We would think if we drop two objects of different weight from the same height the heavier object would fall faster than the lighter object, right? Therefore, we’re saying that the velocity and acceleration of objects depend on their mass. The experiment will explore if that is true or not, if not then we will look at the reasons behind that.
Set-up:
To perform the experiment we used two light sensors, different objects and an NXT “robot” that our professor helped us to program. The program basically allowed the sensors to detect the object and see how long it takes to reach the ground. The distance between the sensors was added to the program in order for the NXT to calculate the velocity of the objects. The picture below illustrates on how does the program work.
The experiment is really easy to do. It’s just placing different objects few centimeters above the first sensor then dropping them.
Result:
To do the experiment we used a book, hat and a paper, and the result we found was that heavier objects had greater acceleration than the lighter ones. Also, we found that air resistance is proportional to the velocity, the more the velocity, the higher the air resistance will be. When we considered the weight, we realized that the more the mass, the lower the effect of air resistance will be. Also the larger the surface area, the larger is the effect of air resistance. This concept can be applied in designing devices like cars, trains and airplanes to reduce the effect of air resistance and increase the speed of the vehicles.
The following like shows the experiment
http://www.youtube.com/watch?v=z_sJ15feNGw
Presenting the experiment to high school students really helped us to understand the concept even more. They did not know how the air resistance relates to our daily life. We had to explain it in different ways to deliver the correct concept to them. Most of them actually thought that the velocity of the falling objects depended on the mass, where in fact it did not. The effect of the air resistance is what really controls the speed of the objects. The students asked questions that opened our minds and made us think more about our experiment. We learned from them as they learned from us. The experience was fun and we had a great time with the students.
Our Presentation:
http://prezi.com/vuxhsvt1desk/falling-objects/
Hyperlinks:
http://www.vernier.com/experiments/psv/40/falling_objects/
http://physics.ucr.edu/~wudka/Physics7/Notes_www/node49.html
http://www.juliantrubin.com/bigten/galileofallingbodies.html