Dynamics Activity
Newton's First Law in a Car


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Demonstrates the First Law in accelerating, decelerating, and turning cars. Demonstrates the purpose of seat belts.


dynamics cart

"Super Dave" figure

concrete block (for collision)

2 rubber bands

wooden block (for seat back)


  1.  Place the figure on the bare dynamics cart. When car accelerates from rest, show that you remain at rest while car accelerates. Add a seat (wooden block held with a rubber band) to show that seat provides the force to accelerate the person.

  2. Crash the cart into the barrier. Show that the person continues to move at the same velocity when the car stops (They aren't "thrown forward.") Add a seatbelt (rubber band) to show that the seatbelt supplies the force to stop you.

  3. Take person out of the seatbelt. Show that as the car turns, the person continues to go straight. (There is no "centrifugal force.")


As above. See also Riding in a Car and Thoughts on Force and Newton's First Law

adapted from Robinson, Conceptual Physics Laboratory Manual, Addison-Wesley, Activity 8 - Buckle Up!

last update November 16, 2009 by JL Stanbrough