Crash Barrier Lab

Forces That Transfer Energy: Making Crash Barriers

Why investigate forces that transfer energy? In automobile collisions, a great deal of energy must be transferred from the car (and its occupants) to other objects and transformed into other forms of energy. Major automobile manufacturers spend millions of dollars each year testing new safety features. Engineers will talk about “energy absorbing materials” and “crumple zones” in new car designs. They take advantage of the fact that materials transfer energy in different ways and at different rates. In order for a moving car to stop, its kinetic energy must be transferred to another object and/or transformed into another form of energy. When the car stops, it has no KE. Where does the energy go? How is energy transferred to an object or away from an object? Forces are responsible for the transfer of energy. The forces are defined as pushes or pulls. In many cases the direction of the force is important in determining whether the force will transfer energy to an object or away from an object. We will be investigating this relationship between force and energy transfer in the following parts of the investigation.

Crumple Zones

Collapsed Crumple Zone

Good Crumple Zone

Investigating How Forces Transfer Energy Part A: Creating a Barrier Focus Question: What barrier design will stop the car in the shortest distance? Your task is to create a stopping barrier out of dominoes that will stop the car in the shortest distance possible.

The Purpose/Goals Your group will investigate the relationship between force and energy transfer in a lab. Your group will engineer a free standing crash barrier out of dominoes that will stop the car safely in the shortest distance possible. Connection to the real-world: Your group will connect why it is important for mechanical engineers to test different construction materials/safety materials when considering the design and construction of cars. **ie. Where cars should have crumble zones that absorb energy so that it is not impacting the people inside the car. Your group will construct an energy chain of the transformation of energy into different forms and the transfer of energy in the crash barrier lab. Essential Question: How can energy be transferred from one material to another? What happens to a material when energy is transferred to it?

Before You Begin What is the independent variable? You are expected to answer these questions by conducting a scientific investigation. We know that when conducting an investigation it is important to clearly identify which variables will be changed and which variables will not be allowed to change. What is the independent variable? What is the dependent variable? What factors/variables must be held constant? Hypothesize how a shorter stopping distance would affect the amount of energy produced?

Design of the Investigation: What CAN Change: You can change the number of blocks in the barrier and the way the blocks are arranged, but the barrier is the only thing that should be changed from trial to trial. If we want to make fair judgments about how effectively each barrier stops the car, than we need to ‘control’ all the other possible variables. Only the barrier should change. Everything else (the car, the ramp, the car’s KE, etc.) needs to remain the same.

Notes of Love and Stipulations from Mrs. C Add the stipulation that the first domino must be placed upright. This minimizes the chance for the domino to get wedged under the car. When the car is not on the track, turn it over so that it does not roll off of the table. This will happen even with the most careful students. Make sure that students use the “non plunger end” of the car to impact the barrier. Make sure your jot down your findings on what works and what fails to work in your Crash Barrier Design.

Your Mission… You will answer the pre-lab questions (1-4) BEFORE you start the lab. 2. Practice three or four times before you record your trials. 3. You will stack the dominos at the 60cm mark on the ramp. 4. Draw your design in your table. 5. Record the distance in cm from the 60cm mark to the first domino. 6. If your dominos touch the end wall, your trial doesn't count! 7. You can not have any dominos touching the black wall at the end of ramp.

When you finish… Draw your best crash barrier design on the giant white boards. Explain why this design worked the best for you. Be prepared to report out about the essential questions and purpose of the lab. (See paper at your lab station)

If you finish early… ***If you finish early… try using a domino (or if you brought an army man, polly pocket etc.) and use it as a passenger in your vehicle. Try to stop the car in the shortest distance without your passenger falling off!!

Wrap-Up Wrap-Up- Create an energy chain showing one downhill trial of your car. Be sure to use your vocabulary! Ie. PE, KE, transformation, transfer, various forces etc. Use your Notes 22 for examples.

Lesson Extension Extension of lesson: Connection to Dover Nascar: How do SAFER (steel and foam reduction) barriers absorb energy and help product racecar drivers?

Can we calculate the energy transfer? If Force= mass * acceleration and Work= Force* distance Could we potentially determine the amount of energy transferred to the dominoes if we know the mass and acceleration of the car?