Purpose
The purpose of this experiment was to demonstrate the law of conservation of energy; a law that states that energy is only transferred and transformed and never destroyed.
Procedure
In order to do this experiment, our trial team used a 3 beam balance to measure and record the mass of 4 different amounts of water. For each amount of water, we used a funnel and stopper to pour the water from a constant height of 73 cm. onto a waterwheel of plastic spoons. The force of the falling water would in turn make the wheel spin, and we would observe and record for each trial the number of rotations the wheel spun, and for how long it spun.
Calculations
For each trial, we are left with a water mass, a distance, a velocity, a number of rotations, and a time. For each trial, we first used this data to calculate the Potential energy in the system before the water was poured. Then, we would be left with a value of energy in Joules. We used the formula PE= mgh for this calculation. For example, Trial 1 was calculated as follows:
PE= mgh = 0.3731kg x 9.8m/s^2 x 73cm = 266.92 Joules
The second calculation made for all four trials was Kinetic Energy. This calculation used the same set of measured data to derive the amount of energy exerted on the waterwheel in terms of mechanical energy, or energy of motion. The formula used for this step was KE= (1/2)mv^3 . In this formula, m is mass and v^3 is velocity cubed. So, the kinetic energy in Joules for trial 1 was found as follows:
KE= (1/2)mv^3= (1/2)(.3731kg)(14.6m/s^3)= 580.57 Joules
The third calculation was intended to derive the power of the spinning wheel for each trial, but the equation provided was unclear. (.5 x 1000kg/m^3 x 2.24m x velocity^3) I could not determine the proper order of operations in using this formula.
Results
PE KE
Trial 1 266.92J 580.57J
Trial 2 156.60J 665.28J
Trial 3 108.10J 235.12J
Trial 4 36.41J 1237.5J
Analysis
- As you change the mass of the water, what changes do you see to the energy?
The mass of the water decreases with every additional trial. So, I can tell that as the mass of the water decreases, both the potential and kinetic energy in the system decrease, with the exception of KE in trial 4. I would consider this discrepancy due to human error. Aside from this, the water mass and the energy in the system seem to have a positive relationship.
2. Do you think energy can be a big amount with a little amount of water?
I do think that this is possible. I recall that both PE and KE are also dependent on either height (h) or velocity (v). If either of these values are increased enough, you can have a high amount of energy in the system with a relatively small amount of water.
3. Will there be more energy if there is more water, or more water?
As more water is poured onto the wheel, there is more potential energy that is converted into kinetic energy as it falls.