Why Do We Wear Seatbelts?

Learning Resource Type

Learning Activity

Subject Area

Science

Grade(s)

8

Overview

The activity can be used to introduce Newton's first law of motion. The teacher will demonstrate the different ways in which a car can roll down a ramp and the resulting effects of each trial. The students will perform a quick write before each trial to make predictions about the outcomes. The students will also explain why the trials were different after the car was rolled three times. Newton's first law and inertia are the focal points of this activity.

This activity is a result of the ALEX Resource Development Summit.

Phase

Before/Engage
Science (2015) Grade(s): 8

SC15.8.8

Use Newton’s first law to demonstrate and explain that an object is either at rest or moves at a constant velocity unless acted upon by an external force (e.g., model car on a table remaining at rest until pushed).

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Vocabulary

  • Sir Isaac Newton
  • Newton's First Law of Motion
  • Constant velocity
  • Balanced force
  • Unbalanced force
  • External force
  • Rest
  • Motion
  • Inertia

Knowledge

Students know:
  • An object at rest remains at rest unless acted on by an external force.
  • An object in motion remains in motion unless acted upon by an external force.
  • Inertia is the tendency of an object to resist a change in motion.
  • An object subjected to balanced forces does not change its motion.
  • An object subjected to unbalanced forces changes its motion over time.
  • Constant velocity indicates that an object is moving in a straight line at a constant speed.

Skills

Students are able to:
  • Demonstrate Newton's first law.
  • Articulate a statement that relates a given phenomenon to a scientific idea, including Newton's first law and the motion of an object.

Understanding

Students understand that:
  • Newton's First Law states that an object at rest remains at rest unless acted upon by an external force.
  • Newton's First Law states that an object at in motion remains in motion at a constant velocity unless acted upon by an external force.

Scientific and Engineering Practices

Constructing Explanations and Designing Solutions

Crosscutting Concepts

Cause and Effect

Learning Objectives

I can use Newton's first law to explain why an object behaves the way it does whether in motion or at rest.

I can explain that inertia is the reason we wear seat belts.

Activity Details

The teacher will set up a ramp in the classroom so that all students can see a whole group demonstration using a toy car. The teacher will roll a toy car down the ramp three different times for three different trials. Before each trial, allow the students one to two minutes for a quick write about what they think will happen when the car is rolled using the Why Do We Wear Seatbelts? document. The first time the car will roll along the ramp with an action figure sitting loosely on top of the car and will not hit anything before it rolls to a stop. The second time a brick or block will be placed at the end of the ramp that will cause the car to come to a sudden stop when the car is rolled down the ramp. The action figure will once again sit loosely on top of the car. The third time the car is rolled, the action figure will have a rubber band attaching it to the car, and the car will again roll into the brick or block causing it to come to a sudden stop. After observing all three trials, the students should complete their Why Do We Wear Seatbelts? document.

The teacher may then wrap up the learning activity with a group discussion. Possible questions could be as follows:

1. How and why was the outcome of each trial different?

2. How does this relate to seatbelts? Why should we wear seatbelts?

Assessment Strategies

Assess student learning through written answers on the Why Do We Wear Seatbelts? document and class discussion. This learning activity is an introduction to Newton's laws, and this activity can be used to gauge the prior learning of students and as a guide to future lessons and/or activities.

Variation Tips

The teacher can vary the angle of the ramp to make the car go faster or slower. The teacher could allow students to design other methods of protecting the action figure during a crash. Allow students to come up with ideas to protect the action figure and then allow a class vote to select the best design. Conduct another trial with the winning design.

Background / Preparation

The teacher will need to construct a ramp and allow enough space at the end of the ramp, so the car can continue to roll until it runs out of inertia. The teacher needs to provide a car and an action figure. (Make sure the action figure can ride on top of the car without falling off unless it strikes the brick/block.) The teacher can either print the Why Do We Wear Seatbelts? document or share with students electronically.

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