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# Minimizing Forces During a Collision

A Carolina Essentials™ Activity

## Overview

Many students have had the opportunity to participate in an egg drop activity in which they design a container to protect an egg dropped from a designated height. In this activity, students design a car “bumper” to absorb the force of a pendulum colliding with a frictionless cart. Students utilize and apply concepts including force, energy transformation, conservation of energy, momentum, conservation of momentum, and Newton’s laws of motion. A well-designed bumper should absorb the force of the pendulum striking it, resulting in minimum displacement of the car. This activity can also be used as a design challenge after students research automotive safety design and technologies like air bags, crumple zones, and seat belts.

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Teacher Notes
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Student Worksheet
Grade & Discipline
9-12

Physical Science, Physics
Recommended for grades 9-12.

Time Requirements
Prep20-30 min
Activity45-60 min

Teacher Prep time: 20-30 min
Student Activity: 45-60 min

Safety Requirements

## Overview

Many students have had the opportunity to participate in an egg drop activity in which they design a container to protect an egg dropped from a designated height. In this activity, students design a car “bumper” to absorb the force of a pendulum colliding with a frictionless cart. Students utilize and apply concepts including force, energy transformation, conservation of energy, momentum, conservation of momentum, and Newton’s laws of motion. A well-designed bumper should absorb the force of the pendulum striking it, resulting in minimum displacement of the car. This activity can also be used as a design challenge after students research automotive safety design and technologies like air bags, crumple zones, and seat belts.

Save & Print
Teacher Notes
Save & Print
Student Worksheet

## Phenomenon

Look at the photograph of this front-end wreck carefully. What would you ask the automotive engineer about the design and construction of this car?

## Essential Question

What general characteristics must be engineered to minimize the force on an object during a collision?

## Activity Objectives

1. Generate and evaluate evidence describing the magnitude of force when a collision occurs.
2. Design, test, and refine a modification for the Hall’s car to minimize the force on the car during a collision.

## Next Generation Science Standards* (NGSS)

PE HS-PS2-3. Apply scientific and engineering ideas to design, evaluate, and refine a device that minimizes the force on a macroscopic object during a collision.

### Science and Engineering Practices

#### Constructing Explanations and Designing Solutions

• Apply scientific ideas to solve a design problem, taking into account possible unanticipated effects.

### Disciplinary Core Ideas

#### PS2.A: Forces and Motion

• If a system interacts with objects outside itself, the total momentum of the system can change; however, any such change is balanced by changes in the momentum of the objects outside the system.

#### ETS1.C: Optimizing the Design Solution

• Criteria may need to be broken down into simpler ones that can be approached systematically, and decisions about the priority of certain criteria over others (tradeoffs) may be needed.

### Crosscutting Concepts

#### Cause and Effect

• Systems can be designed to cause a desired effect.

## Safety Procedures and Precautions

Students should wear safety glasses and avoid unintended contact with the swinging stopper.

## Teacher Preparation and Disposal

To save set-up time, prepare materials for each table. You may construct the pendulum before the activity then store a permanent class set.

#### Teacher

A. Pendulum Construction

1. Student: Place the support stand ring about 8-10 inches from the top of the support stand rod and tighten securely.
1. Teacher: You may wish to tie the stoppers yourself to save some time. The size of stopper can vary between groups but needs to remain the same within a group.
1. Thread the string through the smaller end of one hole of the stopper and then back up through the second hole and tie the string securely.
1. Check groups to ensure the stopper is colliding with the back of the car.
1. Tie the stopper pendulum to the ring so the stopper will contact the Hall’s car on the flat, narrow side of the car, (back side).
1. Place the set-up on the floor so there is room for the car to travel.

B. Initial State Testing

1. Place the back end of the car directly next to the base of the ring stand so the stopper will collide with the back side of the car.
1. Make sure there is adequate floor space for the cars to travel unimpeded.
1. Keeping the string taut, raise the stopper pendulum until the string is parallel with the floor. Measure the distance from the floor to the stopper in centimeters.
1. Release the stopper so it hits the car.
1. Measure the distance the car travels from the base of the pendulum in centimeters.
1. Repeat the procedure for a total of five trials.

Design a Bumper

1. Using the materials available, design, test, and refine a force absorbing bumper for the Hall’s car.
1. Allow students to try materials before deciding on a design to test.
1. Test your design and refinements at least five times.
1. Pictures can be inserted into the activity write-up.
1. Take a picture or sketch your final design.

## Data and Observations

Design Evaluation Data

## Analysis & Discussion

Use the engineering design cycle as a framework, your data, and physics concepts to make a written recommendation for directions to reduce force on the Hall’s cart during a collision.

Student answers will vary but must include all tasks within the design cycle and the evidence to support their revisions.

Use what you have learned through the engineering process as evidence to explain why the car in the phenomenon picture has a crumpled front end but an in-tact driver’s compartment.

Student answers will vary but must include evidence generated during the engineering process applied to the picture of the wrecked car.

*Next Generation Science Standards® is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.

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