Lesson: Free-Body Diagrams Physics • 9th Grade

In this lesson, we will learn how to analyze free-body diagrams and use them to determine the net force and unknown forces acting on objects.

Lesson Plan

Students will be able to

use a free-body diagram to determine the resultant force on an object,
use a free-body diagram to determine the magnitude of a given force acting on an object.

Lesson Video

Lesson Playlist

04:16
06:07

Lesson Worksheet

Q1:

In which of the following diagrams do the directions of all the vectors shown correctly represent the vectors in a free-body diagram of the forces acting on Earth due to the Sun’s gravity?

Q2:

The wheel of a car is rotating counterclockwise. The car is accelerating horizontally. The wheel makes contact with the road beneath it at a point that lies on the surface of the wheel, as shown in the diagram.

Which of the following is a correct free-body diagram showing the forces acting on the point ?

Q3:

A box is pulled along a surface by an upward diagonal applied force of 55 N, as shown in the free-body diagram. The object does not move.

Is the magnitude of the reaction force greater than, less than, or equal to 75 N?

Is the magnitude of the friction force greater than, less than, or equal to 55 N?