Minimizing Forces During a Collision

A Carolina Essentials^TM Activity

9-12

High School

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.

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?

Red Wrecked Car With Smashed Crunched Nose

Essential Question

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

Activity Objectives

Generate and evaluate evidence describing the magnitude of force when a collision occurs.
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 & ENGINEERING PRACTICES

Constructing Explanations and Designing Solutions

DISCIPLINARY CORE IDEA

PS2.A: Forces and Motion

ETS1.C: Optimizing the Design Solution

CROSSCUTTING CONCEPTS

Cause and Effect

Materials

1 Support stand with ring/ group
1 Hall’s Car-Frictionless cart/ group
1- 2-hole stopper size 8, 9, or 10/ group
60 cm of String/ group
Metric ruler
Duct tape to affix the bumper to the Hall’s cart
Rubber bands to affix the bumper to the Hall’s cart
Bumper materials (examples include: balloons, cotton balls, packing peanuts, water, paper, facial tissue, other items students request, and snack size resealable bags for housing bumper materials)

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.

SCIENCE & ENGINEERING PRACTICES

A. Pendulum Construction

1. Place the support stand ring about 8-10 inches from the top of the support stand rod and tighten securely.
2. 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.
3. 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).
4. 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.
2. 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.
3. Release the stopper so it hits the car.
4. Measure the distance the car travels from the base of the pendulum in centimeters.
5. 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.
2. Test your design and refinements at least five times.
3. Take a picture or sketch your final design.

TEACHER PREPARATION AND TIPS

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.
Check groups to ensure the stopper is colliding with the back of the car.

Make sure there is adequate floor space for the cars to travel unimpeded.

Allow students to try materials before deciding on a design to test.
Pictures can be inserted into the activity write-up.

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.