Lesson: Newton’s Third Law of Motion Mathematics

In this lesson, we will learn how to solve problems on Newton’s third law.

Lesson Plan

Objectives

Students will be able to

recall and state Newton’s third law of motion,
calculate reading on scales in an accelerating system,
find the acceleration of a system given the reading on a scale contained in the system,
combine all of Newton’s laws of motion.

Prerequisites

Students should already be familiar with

resolving forces on a body,
Newton’s first and second laws of motion.

Exclusions

Students will not cover

problems containing pulleys.

Lesson Video

Lesson Explainer

Sample Question Videos

02:44
02:09
01:55

Lesson Worksheet

Q1:

An elevator is accelerating vertically upward at 2.6 m/s². A man of mass 124 kg is standing inside. Determine the reaction force of the floor on the man.

Q2:

A body of mass 87 kg was placed inside a box of mass 60 kg which was attached to a vertical string. A tension of 265 kg-wt was applied to the string causing them to rise vertically. Determine the force exerted by the body on the base of the box while they were rising upwards. Take .

Q3:

An elevator was accelerating vertically downward at 1.7 m/s². Given that the acceleration due to gravity is , find the reaction force of the floor to a passenger of mass 103 kg.