Lesson: Static Friction Physics • 9th Grade

In this lesson, we will learn how to analyze the forces acting on objects on frictional surfaces that are required to induce motion in the objects.

Lesson Plan

Students will be able to

define the coefficient of static friction using , where is the magnitude of a force applied parallel to a surface and is the angle made by the surface with the horizontal,
understand how to determine the static friction force on an object,
calculate the coefficient of static friction between two surfaces.

Lesson Video

Lesson Playlist

04:06
02:16

Lesson Worksheet

Q1:

The figure shows two blocks, block A and block B. Block A is on a rough surface, and block B is on block A. A force acts on block A, parallel to the surface. Initially, block A does not move, and is steadily increased. When has increased enough to make block A start to move, both blocks move in the direction of , but block A has a greater acceleration than block B. Which of the following is a correct statement about the relation of , the coefficient of static friction between block A and the surface, to , the coefficient of static friction between the blocks?

Q2:

A brick is initially at rest on top of a rough horizontal surface, as shown in the diagram. The brick is pushed by a force parallel to the surface and starts to move. The coefficient of static friction of the brick with the surface is 0.75. What must the weight of the brick, , be less than?

Q3:

A brick is initially at rest on top of a rough horizontal surface, as shown in the diagram. The brick is pushed by a force parallel to the surface and starts to move. The weight of the brick . What must the coefficient of static friction of the brick with the surface be less than?