2. Inverse square laws. The butter gun.

3. A nutty professor invents a butter gun It sprays melted butter onto toast. When the trigger is pulled, a fixed amount of butter is emitted.

4. Thickness of the butter. The professor can spray one slice of toast from 1m distance ! The butter is too thick ! How many pieces can he spray from 2m distance ? What is the comparative thickness ?

5. 2m 1m

6. Pieces of toast-square relationship Distance of gun 1m 2m 3m 4m 5m Toast spread 1 4 9 16 25

7. Comparative thickness of butter Distance 1m 2m 3m 4m 5m Thickness 1 1/4 1/9 1/16 1/25

8. This relationship is called the inverse square law. It applies to: Gravitational strength with distance. Electrostatic force with distance. Light intensity from a point object. Sound intensity from a point source. Nuclear radiation from a point source. –Assuming that the light sound and radiation is not absorbed as it travels!