1. Come up with a list of measurable physical characteristics that may affect the outcome of a "race" and create a hypothesis for how each might affect the result.
2. Design a series of experiments that will allow you to test your hypotheses.
3. Synthesize your results to create a model that will allow you to predict the winner of a race between two rolling objects.
4. Explain how your results relate to the Law of Conservation of Energy.
Key terms:
- energy
- velocity
- speed
- hypothesis
- conservation
- radius
- mass
Pre-Lab Discussion and Explanation: In this lab, we are trying to relate the different conditions of our lab to the Law of Conservation of energy. The law, which involves kinetic and potential energy, states that the energy of a system cannot be created nor destroyed, but simply transformed. In this lab, the controls in our experiment are two balls with the same diameter, mass, and distribution of mass.
Let's Get Right to it - The Races:
Race 1: Different Masses
- 24 g ball vs. 94.9 g ball
- Same radius
- Same distribution of mass
- Hypothesis: The mass of the balls will not affect the speed
In this experiment, we proved that a difference in mass does not affect the race. Both balls reach the bottom of the ramp at the same time.
Race 2: Distribution of Mass
- Mass doesn't matter (proven earlier)
- Hypothesis: a different distribution of mass WILL affect speed
Race 3: Different Diameters
- Mass does not matter (proven earlier)
- Hypothesis: The radius of the balls WILL affect the speed, meaning one will go faster
Analysis:
Question: How does this relate to the Law of Conservation of Energy? Did we break the law? Are we going to physics jail?
Answer: First off - no, we didn't break the Law of Conservation of Energy, and no, we aren't going to jail. The Law of Conservation of Energy involves gravitational potential energy (m*g*h) and kinetic energy (1/2*m*v^2).
In the lab, we had potential energy converting into kinetic energy. The kinetic energy will be in two forms: translational (1/2*m*v^2) and rotational kinetic energy (1/2*I*w^2). If an object has a larger translational kinetic energy, it will have a small rotational energy. For example, a solid disk has a smaller rotational energy.
An equal distribution of mass and an object with greater diameter travel as a greater speed than their opposing object. In our lab, we believe that the increase in speed is due to a greater moment inertia, or I, relating to the torque of the object. To photos below will be able to explain and walk through the translation:
