This lesson focuses on two elements: understanding Newton’s laws of motion, and how to use Newton’s laws to create force diagrams. This lesson also demonstrates how to incorporate requirements of the Next Generation Science Standards (NGSS) into a physics lesson. It uses a discrepant event (phenomenon) to model forces at work on an object resulting in motion. Students should be familiar with Newton’s laws and have a basic understanding of forces. This lesson utilizes basic lab equipment (masses, spring scales, and thread/string) and can be completed in one full period, depending on the length of period.

The Performance Expectations of this lesson are:

• HS PS2-1: Motion and Stability, Forces and Interactions
• Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.

The Objectives of this lesson are:

• Students will apply their understanding of Newton’s Laws to predict the outcome of a demonstration.
• They will develop a model to explain the cause and effect of two strings being pulled with unequal forces acting upon 2 identical masses.
• They will plan and conduct an investigation to find evidence to validate their claim.