In this video, we will explore a simple activity to demonstrate that surface area of a sphere is 4πr^2 using simple and readily available material.

We will use a tennis ball as the spherical object. The diameter of the ball is measured using two flat card boards. The radius (r) can be calculated by diving the diameter by 2.

Stick some glue on one end of the ball and cover the whole ball with a thread. When the ball is completely covered from end to end, cut the other end of the string. Open this string and keep it aside.

Draw four circles on a paper with the radius r. Arrange the string that was used to cover the ball in a tight spiral in these circles. You will notice that the sting exactly covers area occupied by four circles with radius r.

We know that area of circle is calculated using the formula πr^2. Surface area of a sphere with the same radius is equal to four such circles i.e. 4πr^2.

To understand this concept mathematically, watch the following video:
But why is a sphere's surface area four times its shadow? By 3Blue1Brown:

[ Ссылка ]

We hope you enjoyed this experiment and learned something new. For more such hands-on science and mathematics activities subscribe to our YouTube channel IISER Pune science activity Centre.

Presented By: Sarika Jeevan Patil, Huzurpaga Katraj Secondary School, Pune


Produced by: IISER Pune Science Activity Center
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