OVERVIEW: This lesson is to help students more fully understand the relationship between Potential and Kinetic energy. Students should already know the definitions for work and mechanical energy.
PURPOSE: Students will observe and record the amount of work done by the three different marbles rolling down an inclined plane and hypothesize about the reasons for the differences.
OBJECTIVE(s): Students will:
Discover that the larger the mass, and the higher an object is raised, the more energy is stored. Measure work in centimeters. Compute the average distances. Make predictions, record observations, and create hypothesis. RESOURCES/MATERIALS: 3 marbles (Different sizes &/or weights), inclined plane, metric ruler, milk carton.
ACTIVITIES AND PROCEDURES:
Exploration/Explanation: Set up a demonstration of rolling three different sized marbles down an inclined plane. Place the bottom section of a milk carton at the bottom of the ramp to catch the marble and measure the distance that it moves the carton.
Ask questions below before demonstration.
- Who can tell me the meaning of work?
- What is mechanical energy?
- Which marble has more mechanical energy? (sitting on flat plane)
- If I put the marbles up on the inclined plane, would they have energy? Why?
This energy is called potential energy. (PE) Energy at the point of release, or stored energy. The energy of a moving object is Kinetic energy. (KE) PE changes to KE as the marble rolls down the ramp.
- Which marble do you think has the most PE?
- Ask students to predict how many centimeters each marble will move the milk carton, and which marble will move it the most. (write on a piece of paper)
Demonstrate one marble and record the distance the milk carton was moved. Repeat five times and take the average distance. Demonstrate the second and third marbles using the same process.
Compare students predictions with outcomes.
- Which marble had the most energy? Why?
- What would happen if the smaller marble was let go at twice the height of the larger one? Why? (Demonstrate)
TYING IT ALL TOGETHER:
- What are some examples of storing and using energy in our environment? (Teeter-totter, Wrecking ball, Hydroelectric dam, Elevators)
- What factors affect the amount of work an object can do? (Mass and Height)
On the paper that students wrote their predictions, have them explain why their predictions were right or wrong.