Baseball and string activity to find the surface area of a sphere
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Objectives
Estimated Time
1 hour
Prerequisites/Instructions, prior preparations, if any
Circles should have been covered.
Materials/ Resources needed
Non digital: Baseballs, string, marker pens, scale, scissors and chart paper
Digital: Computer and projector
This activity has been taken from the website ehow.com
Process (How to do the activity)
- Process:
- Divide the class into groups and give each group a baseball and string.
- Ask the students to lay flat the string around the widest part of the baseball and mark.
- The meaured length would be the circumference.
- The measurement will be divided by pi to find the diameter (Remember: circumference/diameter = pi).
- The diameter divided by 2 would be the radius. Note down the radius.
- Now take a long piece of string and carefully wind it around the entire surface of the ball taking care not to overlap.Cut and discard the extra string.
- Next unwind the string,measure it using a measuring tape. This measure would be teh surface area of the sphere.
To understand the formula Failed to parse (syntax error): {\displaystyle 4πr^2} for deriving surface area of a sphere :
- Consider the length of string obtained from step 7 , divide it into exactly 4 equal parts.
- Make a circle with each part. Measure the radii.( Hint: Can draw circle of radius from step 5 and lay the string around it)
- Observe that 4 circles would be equal and the radii in all 4 cases would be the same as the radius of sphere (derived initially by measuring circumference).
- The length of string covering the entire surface area of the sphere has been formed into 4 circles of equal radius.
- The area of 1 circle is Failed to parse (syntax error): {\displaystyle πr^2}
- The area of 4 such circles would be 4 times the area of such circle.
- Hence teh area of a sphere would be Failed to parse (syntax error): {\displaystyle 4πr^2}
- Developmental Questions
- Evaluation
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