Monthly Archives: December 2011

Balloon Rocket Lab!!

Work is the application of force over distance. For example, if I lift a soccer ball off of the field, and carry it over to my locker, I am doing work. The formula for work is Work = force x distance. Work is measured in Joules (J).

Power is measured in Watts (W). It’s formula is Power = Work/Time. “Power is the rate at which energy is transferred, used, or transformed.”- Wikipedia. Continuing the example with the soccer ball, if it took me 2 minutes to get the soccer ball to the locker, to measure the power, it would be work/2 minutes (time). Energy is the ability to do work. The types of energy that would apply to this Balloon Rocket lab is, kinetic energy, thermal energy, potential energy, elastic potential energy, and sound energy. But, only kinetic energy and elastic potential energy helps the movement of the balloon. Energy is also measured in Joules (J).

The gravitational force and the normal force were equal in this lab experiment. The thrust force is greater than the friction because it is what makes the balloon move forward. If the thrust force is larger, it travels. If the friction was larger, the balloon wouldn’t move because it would be held behind. In the second image, the trust decreases since the balloon eventually stops.

<——- ——->
This would be the reaction force pair. This is because the balloon is releasing air on the left side of the string, but it is moving horizontally to the right side. This is why the reaction force pair consists of two arrows going opposite ways.  It symbolizes the  movement of the balloon across the string, releasing air to the right side.

The air that is leaving the balloon, has air that is pushing against it too, this makes the balloon move forward. The air is pushing on the balloon to create movement.

This is my video:

The method:
1.) Tie a string onto two areas.

2.) Put the string into the straw.

3.) Blow up the balloon.

4.) Tie the balloon to the straw.

5.) Let go and record the balloon.

6.) Repeat this step 5 times.

The controlled variables are the amount air you pushed into the balloon, and the point at the string where you started the balloon rocket. Also, the straw, length of string and tape are other controlled variables. In this experiment, we were not looking for differences or changes, so there were no independent variables.  The dependent variable is the work of the balloon.

The mean distance for this data is 5.50m and the mean time for this 1.5s.

The weight was 1.5 grams. The mean work is force x distance. The force is 1.5g x 10N which is 15N. So, 15N x 5.50M = 82.5 J. The work was 82.5 J.

The power is calculated work/time. 82.5 J/1.5s. This equals 55 W.

The uncertainty for the distance is ± 0.01. The uncertainty for the weight of the balloon is ± 0.01. Finally, the uncertainty for the time of the travel is ± 0.01.

We measured the time of the balloon to travel with a stopwatch, and the distance the balloon travelled with a meter stick.

This data is fairly accurate and reliable. I noticed that the data I received were closely related to each other, the range was not far. One down point was the size of the balloon, was different each time, even though I used to same amount of blows to fill it up. This also makes it somewhat unreliable.  The data is valid though, since I received the data that worked, and it gave me a valid work and power.

Elastic potential energy is the potential energy stored in the change of an elastic object. This elastic potential energy transformed into elastic energy, kinetic energy, sound energy, thermal energy.

Lost energy is found in the beginning, since the air from the balloon is distributed in different paths. Also, the amount of air released is uneven. Energy is also lost by the friction caused between the string and the straw.  Efficiency is the ability to accomplish a job with a minimum expenditure of time and effort. (Dictionary.com, 2011). If we were to do this experiment once again, I would change some of the measuring tools we used, such as straw. We could have used smaller, thinner, and shorter straw to reduce the energy lost due to friction. Also, the meter stick, which we used to measure the distance the balloon travelled. A tape measure would have been more efficient and accurate.

To extend your conclusion to Level 5-6 for Knowledge and Understanding
The weight of the balloon we used was 1.5grams. The force (thrust) is 15 Newtons. This is the thrust force of our ballon. Calculating this, the assumption of the balloons force being 0.5N, is wrong. There is a great difference between 15N, the accurate thrust force, and the assumed thrust force of 0.5N. The assumed thrust force is way to little, and light.
Bibliography
Elastic potential energy. (n.d.). Retrieved from
http://hyperphysics.phy-astr.gsu.edu/hbase/pespr.html
Taylor, S. (n.d.). “How is energy used to produce change?”. In Energy, work & 
       power. Retrieved December 14, 2011, from http://i-biology.net/myp/
intro-physics/energy-work-power/

What is power?
 (2011). Retrieved from http://www.asknumbers.com/WhatisPower.aspx
Work [Image]. (n.d.). Retrieved from http://share.ehs.uen.org/node/7875
Criterion B:
Criterion C:
Criterion F:
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