Acceleration of a Wheel and Axle
Summary
A lab investigation of an accelerating object can be difficult without motion sensors or computer photogates. The accelerating object can gain velocity in such a way that it moves a great distance in a short time. Using a wheel and axle will slow the motion down so that it can be timed with a stopwatch, and last from 10 to 20 seconds.
CollapseLearning Goals
Students will create their own wheel and axle using cardboard for the wheel and a wood dowel for the axle. Students will observe and analyze an accelerated motion mathematically. Critical thinking will be required for error analysis of the data.
Context for Use
This is a grade 11or 12 Physics activity. It should be done near the beginning of a unit on kinematics or motion in one dimension.
Vocabulary:
-Velocity
-Displacement
-Acceleration
The activity can easily be adapted for grade 8 or 9 physical science.
Description and Teaching Materials
A circular wheel is drawn with a compass or by tracing a circular object. A small hole is punched in the center for insertion of a 6 to 8 inch dowel of diameter 1/4 inch or so. The dowel should fit tightly, so as the dowel rolls along the ramp, the wheel must spin and does not slip. The ramp is made by propping up two meter sticks with a small stack of books on one end, and a slightly larger (maybe 1 book) stack on the other end. The angle should be kept small, under 4 degrees, to prevent slipping of the wheel and axle. It must roll along the ramp. Students should pre-measure a distance, and time the roll. It is important to release from rest so that initial velocity is zero!
Calculation of acceleration can be done using multiple kinematic equations. Different angles can be investigated. If rotational kinematics is being studied, calculations of alpha, I and omega can be brought in.
Calculation of acceleration can be done using multiple kinematic equations. Different angles can be investigated. If rotational kinematics is being studied, calculations of alpha, I and omega can be brought in.
Teaching Notes and Tips
Do not let the angle exceed 4 degrees. Slippage may occur at spots, disrupting the pure rolling motion. I like to have them calculate a in mutiple ways, verifying that all produce the same result.
Assessment
Evaluate the correctness of the calculated values. Check that all methods agree. Look for a pattern of increasing a as angle increases.
Standards
Strand I . History and Nature of Science, Sub Strand B. Scientific Inquiry, Standard1- The student will design and complete a scientific experiment using
scientific methods by determining a testable question, making a
hypothesis, designing a scientific investigation with appropriate
controls, analyzing data, making conclusions based on evidence and
comparing conclusions to the original hypothesis and prior knowledge.
2. The student will distinguish between qualitative and quantitative
data.
3. The student will apply mathematics and models to analyze data and
support conclusions.
4. The student will identify possible sources of error and their effects on
results.
scientific methods by determining a testable question, making a
hypothesis, designing a scientific investigation with appropriate
controls, analyzing data, making conclusions based on evidence and
comparing conclusions to the original hypothesis and prior knowledge.
2. The student will distinguish between qualitative and quantitative
data.
3. The student will apply mathematics and models to analyze data and
support conclusions.
4. The student will identify possible sources of error and their effects on
results.