#3 Creative Lab Opportunity

     In 7th grade science, we have been talking about kinetic and potential energy. The students, in answering my questions about their Rube Goldberg projects, seemed hesitant to answer the questions about the relationship between mass, kinetic energy and velocity.  So... I found some boards, nails, rubber bands, and a box of washers in the back room and designed an experiment for the students. The data that needed to be recorded and the questions to by questions were uploaded into Schoology for students to complete on their computers and turn in. The students had a blast with this project, because it allowed them to experiment on their own, and get their information, then use that data to explain that relationship between mass, velocity, and kinetic energy. There was deeper understanding after this day of experimenting.

Laboratory Investigation

Relating Mass, Velocity, and Kinetic Energy

Problem: How does a change in mass affect the velocity of an object if its kinetic energy is constant?

Procedure:

1.     In front of the rubber band, place the two washers that have been stuck together.

2.     Pull the washers and the rubber band back about 2 cm. Release the rubber band. The washers should slide down the board.  Practice this until you can make the washers go about the same distance every time.

3.     Mark the point where you pulled the rubber band back to and this will be your launching point for the rest of the experiment.

4.     Launch the double washer three times and measure the distance and record it in a data table.

5.     Repeat step 4. For the stack of 4 washers and record in the table, and again with the stack of 6 washers.

Distance (cm)	2 Washers	4 Washers	6 Washers
Round 1
Round 2
Round 3
Average

Analysis and Conclusions:

1.    What is the relationship between the mass, or number of washers, and the average distance traveled?

2.    What kind of energy was the washers when you held them at the launching point?  How do you know?

3.    After the washers were launched, what kind of energy did they have?

4.    You launched all the washers from the same position. Was the energy the same for each launch?

5.    Assume that the further the washers slid, the greater their initial velocity. Did the heavier group of washers move slower or faster than the lighter group?

6.    If the kinetic energy is the same for each set of washers, what happens to the velocity as the mass increases?