Using up lots of Energy

Our latest unit is Energy. We have learned how energy is transformed in different processes. We learned how to make energy flow diagrams, identify the system, and calculate work. We also learned how to calculate power, and identifying how the energy is transformed in each problem. We learned how to calculate kinetic energy, potential energy, elastic potential energy, and mechanical energy. For a reflection on this unit, we chose an application and had to explain the system, the energy stored, and the energy transformations. I chose cheerleading basket tosses and used Prezi. In my example, air resistance is negligible.

Energy on Prezi

Photo Credits:

1. www.freewebs.com
2. www.sharonanndance.co.uk
3. www3.wallacestate.edu

Busting Myths and Other Dangerous Activities of Physics

For a creative approach to a lab on forces and Newton's laws, our teacher gave us two myths that are commonly accepted. We were instructed to design an experiment for each myth, trying to disprove it. I worked in a group with Matt, Ford, and Blaine.

Myth One: An object always moves in the direction of the net force exerted on it.

Materials:

1. Baseball

2. Baseball Bat

3. Ford

Procedure:

1. Ford will toss the baseball up in the air.

2. Ford will hit the baseball with the baseball bat.

3. We will observe the baseball until it hits the ground.

Prediction: If it is true that an object always moves in the direction of the net force exerted on it and we observe the tennisball after the bat is no longer applying a force on it, the ball should drop straight to the ground or .

Free Body Diagrams:

1. Baseball bat hitting baseball:

2. After baseball bat has hit baseball, while baseball is still in the air:

Sum of the forces:

1. 

2.

Observations: After the baseball bat was no longer applying a force on the baseball, the baseball did not drop straight to the ground or move backward in the horizontal direction. Despite that the only forces working on it were air resistance and gravity, the ball continued to move forward in a horizontal direction, officially busting this myth.

Myth Two: An object always changes its motion if there is a force exerted on it by other objects. 

Materials:

1. Blaine

2. Ford

Procedure:

1. Ford will run full speed towards Blaine who is stationary.

2. We will observe Ford's movement after Blaine applies a force on him.

Prediction: If it is true that an object always changes its motion if there is a force exerted on it by other objects and we observe Ford's collision with Blaine, then Ford's motion will change after hitting Blaine.

Free Body Diagrams:

1. Ford before colliding with Blaine:

2. Ford when force is applied by Blaine:

Sum of the Forces:

1.

2.

Observations: Ford's motion did not change after his collision with Blaine because the force he applied was greater than the force that Blaine applied on him. This myth is officially busted.

Conclusion:

1. Are there any myths you couldn't disprove? Does this mean these myths are proven?

Though my group was able to disprove both myths, if a myth was not disproved, that does not mean it is proven. The experiment that you picked could have just been one case where it works, while there is another that could disprove it.

2. For each of the myths you "busted", explain why people still believe they are true.

These myths are based off of common sense. For myth number one, this is the case most of the times, however, it is not always true in situations such as projectiles. For myth number two, also seems like common sense, but people forget that if the force applied on the object is too small, it will not affect it.

Video of Experiments: