lesson1
The title of the laboratory work: Finding the center of mass of a flat figure
Purpose of the work:
- Find the center of mass of a flat figure experimentally.
Expected results:
- If a figure of an unstandardized size would be pinned at the center of mass point, it will stay in balance.
Teacher’s Guide:
- Divide the students to 3 students in each group.
- Before starting laboratory work, read the safety rules:
- To download the worksheet, please follow this link:
Theoretical part
Center of mass is a point representing the mean position of the matter in a body or system.
Sources:
- Центр масс тел. (2019). Физика. Учебник для 7 класса общеобразовательной школы.
Experimental part
Plumb bob and laboratory stand.
For this experiment we need a plumb bob, it can be made from scratch using hands on materials. For this purpose, we need a thread and a pin.
Step 1.
Measure 10 cm of thread and bind the edges. Stick it to the pin. The plumb bob is ready!
Step 2.
To stick the figure to the stand we need to glue a piece of cardboard to the stand using hot glue, so that we can pin the figure to the stand. In this way, we have something to stick the pin on.
Now we can start the experiment.
Experiment 1. Find the center of mass of a flat figure.
In this lab we need a laboratory stand, plumb bob, stationery pin, flat figure, pencil, ruler.
Step 1.
Mark 3 points at the edges of the figure from different directions and pin them.
Step 2.
Attach the figure together with the plumb bob at one of the points using a stationery pin to the laboratory stand.
Step 3. Using a pencil mark 2 dots where the line of plomb bob crosses the figure, mark the upper and lower dots. Take the figure out and using a ruler connect the dots to a line.
Step 4.
Repeat steps 2 and 3 with other pinpoints at the edges.
Step 5. The lines should cross at one point, that is the center of mass. This point can be called O.
Step 6.
Make sure that the experiment was done accurately, check if the point O is really the center of mass, pin the figure to a pencil at the point O. If everything has been done correctly, the figure stays in balance. Draw a conclusion about that result.
Research part
When deriving conclusions, answer the following questions:
- What is the center of mass?
- How to find the center of mass of a flat figure?
Conclusion
If you locate a flat figure horizontally and pin it at the point of center of mass, then the figure will stay in balance.