Pressure depends on the force applied over an area. Fluid pressure is caused by the constant movement of fluid molecules in all directions. Air pressure changes with elevation, decreasing as you go higher, due to having less air above you. The buoyant force on a submerged object is equal to the weight of the fluid it displaces. Whether an object sinks or floats depends on its density compared to the fluid - objects with a higher density than the fluid will sink, while less dense objects will float.

1. Pressure Page 74 Students will be able to Explain what pressure depends on Describe how fluid pressure changes with elevation and depth Describe the effect of the buoyant force Explain how the density of an object determines whether it sinks or floats

8. 77 Air pressure changes with elevation Why? Water pressure

11. Floating and Sinking Page 82 1912

16. Model 85

17. Changing Density 87

18. Quiz