Lesson: Pascal’s Principle Physics • 9th Grade

In this lesson, we will learn how to use Pascal’s principle to analyze the magnitude and direction of fluid pressure on an object.

Lesson Plan

Objectives

Students will be able to

understand that at a point within a fluid, a force acts in all directions away from the point with the same magnitude in each direction,
understand that at a point within a fluid, a force acts from all directions toward the point with the same magnitude from each direction,
understand that an increase in pressure applied to a fluid from any direction increases the magnitudes of the forces that act at the points in the fluid,
understand that the forces acting from the points in a fluid that is in contact with an object produce a pressure on the object that acts normally on the boundary between the object and the fluid in contact with the object,
use the formula to determine magnitudes of forces applied to objects by fluids and vice versa.

Prerequisites

Students should already be familiar with

Exclusions

Students will not cover

compressible fluids,
quantitative understanding of the flow of fluids due to pressure changes,
particle models of fluids.

Lesson Video

Sample Question Videos

05:02
08:53
07:16

Lesson Worksheet

Q1:

A cubic container holds water. The lid of the container can be pushed downward, exerting pressure on the water in the container. Which of the following statements most correctly describes how the pressure exerted by the water is changed when the lid is pushed downward?

Q2:

A bag attached to an intravenous drip holds saline solution that has a density of 2,160 kg/m³. The bag is 15 cm in height and full to the top. The solution flows from the drip through a hole of area 0.785 cm² and passes through the tube into a cannula that has an opening of area 0.0225 cm².

What is the magnitude of the force exerted by the saline solution at the hole at the base of the drip bag? Give your answer to two decimal places.

What is the magnitude of the force exerted by the saline solution at the cannula? Give your answer to three decimal places.

Q3:

A solid object falls through water of density 1,000 kg/m³. At the instant that the top of the object is 25 cm below the water’s surface, the water exerts a pressure on the top, bottom, and side of the object, as shown in the diagram.

Find .