This lesson focuses on two elements: understanding Newton’s laws of motion, and how to use Newton’s laws to create force diagrams. The 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 (force diagrams) at work on an object resulting in motion. This one demonstration can achieve a deeper understanding of Newton’s laws because students are provided the time to investigate using the three dimensions of the NGSS to explain the phenomenon.

**The objectives of this lessons 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.

**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.

**NGSS-Related Teacher Resources for this Lesson**

- Written: Teacher Guide PDF format, Word format
- Video: Teacher Guide
- Video: Lesson Presented in Live Classroom
- Video: Interview with Live Classroom Teacher and Students
**NGSS Coaching Template**for Teachers Using this Lesson PDF format, Word format- Resources for Science Phenomena