Crash Dummy Investigation
Mrs. Peck's Newton Laws of Motion
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In Mrs. Peck's Conceptual Physics class, the 9th graders were discussing Newton's First Law of Motion. Part of Newton's 1st Law states that an object in motion will continue that state of motion until a net force acts upon it. This law can be illustrated in many ways. However, one of the best ways is using clay crash dummies and applying what they learned to a real world situation......the use of seat belts.
The student's task was to design a clay crash dummy and put it on top of a toy car with no seatbelt. They let the car travel down a ramp until the car's motion was stopped by a textbook. They took measurements of the distance their dummy traveled. Then they increased the height of the ramp thus increasing the velocity of the car. They learned that the crash dummy traveled a greater distance during this part of the investigation.
When asked after increasing the ramp height, why did the dummy travel a greater distance when the car stopped, some of the following replies were given.
Cody T. said "increasing the height made the dummy have a greater velocity because it was traveling down a steeper grade".
Caroline V. said "the dummy was not attached to the car and the car was stopped by the book, but the dummy kept going."
Marcus H. said "the dummy wasn't wearing a seatbelt and he had inertia so he flew off the car."
Amanda E. said "The car hit the book and the dummy flipped off the car because the force of the book acted on the car, but no force acted against the dummy so it continued to fly forward."
WOW, I THINK MY KIDS GET IT! Research states we learn more through hands-on experiences than from a "talking head" (lecture).
The students then designed a seatbelt for their dummy and investigated seatbelt use and inertia. They were asked: Should you use a seatbelt? Click here to see their answers.
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Erin M. said "yes, if you don't wear a seatbelt and get into a crash, your inertia would thrust you forward until you hit something like the windshield or the dashboard, which could injure your head or organs or break your bones!" Laura L. said "yes you should wear a seatbelt becuase you'll keep moving without it." Will S. said "yes because when you are in a car and your are in motion and the car stops you will continue in motion unless you have a force, the seatbelt, to stop you." Rob P. said "yes so you don't continue in motion and get hurt. The seatbelt makes the net force that stops you instead of the dashboard or steering wheel." Nashly B. said "yes, the seatbelts are used to provide safety for passengers whose motion is governed by Newton's first law. The seatbelt provided the unbalanced force which brings you from a state of motion to a state of rest." Joe A. said "yes because otherwise no force is acting on you and you would hit the windshield when the car stops." Brian K. said "you should always wear a seatbelt. Newton's first law is inertia which states an object in motion will stay in motion until a force acts upon it. If you don't wear a seatbelt and you crash, your body's inertia will keep your body moving into the dashboard." Courtney C. said "yes, when you are in a car, say you just hit a tree and you and your car were traveling at 50 mph. When you hit, due to inertia you will keep traveling at 50 mph causing you to hit the steering wheel or windshield, which ever stops you first." |
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