Put your seat belt on kids! – a simple experiment

This blog is for all those mothers who are losing their minds trying to tell their kids how important is for them to stay put in the car and keep their seat belts on with a simple do-at-home experiment. Skye Nicholson was kind enough to edit it for her contribution here. 

Nicholson worked as a high school science teacher in Kansas City and Chicago for 10 years. Then she decided to ‘leave her sanity at the door’ and became a stay at home mom to 2 children. 

“Look Mom!” my son says very proudly from the back seat.  When I turn back to do a quick glance as his unknown accomplishment, I see that he is beaming over the fact that he has unbuckled his car seat and wiggled his arms free.

“Ahhh!” I cry, helplessly flailing my arm towards the back seat as we careen down the highway. “What are you DOING?!? You need to keep your seat belt on!”

Of course he can’t redo the buckle, so I have to pull over and strap him back in while trying to explain the importance of seat belts without terrifying him with gruesome descriptions of car accidents. Hm, if only there was a better way to teach my kid about the importance of wearing his seat belt…

Using materials you probably already have at home, this activity is an easy way to demonstrate INERTIA and the importance of wearing a seatbelt.

Inertia is the tendency of an object to keep doing what it was already doing. (You may remember this from school as “An object in motion tends to stay in motion, and an object at rest tends to stay at rest unless acted on by an outside force.”  Also known as Newton’s First Law of Motion if you want to be Smartypants.) Inertia can be felt anytime you slam on the brakes in the car and everyone feels like they are jerked forward.  You are actually not being “pushed” forward when this happens… but rather your body, which was moving forward just as quickly as the car you are riding in, continues that forward motion until the seat belt stops you.


  • Hot Wheels car (available on any grocery store)
  • Play-Doh (it helps if it is relatively fresh, so it will be more sticky.)
  • Stack of books (or a box)
  • Tape (masking tape works best)
  • Pencil (a pen, marker, or good ole stick will also work)
  • Hot Wheels ramp or track (if you don’t have this, just make one out of cardboard!)
  • Ruler or measuring tape
Materials needed for “Hot Wheels Crash Test Dummy” activity.


  1. Use your stack of books (or box) to prop up your ramp at whatever height you choose.  Tape the ramp in place.
  2. Measure 10 inches from the bottom of the ramp and tape down your pencil.  This is the “brick wall” that the car will crash into. (Here is a great opportunity to practice counting with younger toddlers or reading numbers and using a ruler with the older kids!)

    Tape the pencil to the table 10 inches from the bottom of the ramp
  3. With the Play-Doh build a small “man”, about 1/2 inch tall, to be your crash test dummy.  He does not have to be extravagant or anatomically correct.  I usually build more of a “blob.”  Give him a name.  (We’ll call ours “Mo.”)
  4. Stick Mo onto the hood of the Hot Wheels car. He should be stuck well enough so that he doesn’t just tip off, but not so stuck that he becomes a permanent fixture on the car.

    Mo riding on the hood
  5. Ask your child to make a HYPOTHESIS as to what will happen to Mo when the car crashes into the pencil.  (If they are old enough, they can practice writing and sentence skills by writing their hypothesis down!)
  6. It is time to run the experiment!  Hold the car with Mo on the hood at the top of the ramp and let it go.  You should expect the car to hit the pencil and stop, but Mo continues to move forward off the hood of car and lands some distance in front of the pencil – Mo has INERTIA!  (As with all experiments conducted outside of a highly precise lab environment, it won’t work perfectly every time.  But that’s ok – that’s why we call it “experimentation!”)

    Mo should land in front of the pencil.
  7. Send Mo down the ramp as many times as your child wants. Decide if their guess was correct or not. Older kids may want to change the experiment by raising or lowering the ramp, making Mo bigger or smaller, putting the pencil further away, etc.  This is great scientific thinking! (Each time they change something in the experiment, have them write down their new HYPOTHESIS.)

Now let’s give Mo a “seat belt” and see if that changes his destiny! (Have the kids make a HYPOTHESIS…will he be safe this time?) Use the tape to strap Mo down to the hood of the car, and send him down the ramp again.  (This time he should stay put on the hood of the car.  If not, your seat belt is faulty!)

Mo is buckled up for safety.


Mo, of course, is demonstrating what could happen in a car crash if someone is not wearing their seat belt.  His body has inertia, meaning that even though the car stopped (or possibly even reversed) when it hit the pencil, there was nothing to stop Mo’s body from continuing to move forward. When we gave Mo a tape seat belt, the seat belt provided the force to stop the inertia of Mo’s body.

Pin Away!!

If you too are facing problems trying to get your child to stay put in the car, this experiment is for you! Do leave your feedback in the comments and don’t forget to share.

Read more from Skye Nicholson on her blog Stay At Home Science.

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8 thoughts on “Put your seat belt on kids! – a simple experiment”

  1. I think this is a good experiment for kids to see, even if they are a bit older, to remind them why they need to wear seat belts. I think sometimes it helps to see what could happen without them. Thanks for the idea.

  2. I absolutely love this idea! Thankfully, my 2.5 year old hasn’t attempted to get out of his seatbelt just yet…but I’ll keep this in mind for when he does.

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