4 Groovy Ways to Teach Newton’s 3rd Law

Newton’s Third Law of Motion states that for every action, there is an equal and opposite reaction.

Teaching Newton's Third Law of Motion

Although the explanation of the law is simple, STEMists often find the concept hard to comprehend. How do you demonstrate this law to your STEMists?

Check out these 4 groovy ways to teach your STEMists about Newton’s 3rd law.

Play with Marbles

Using marbles to teach Third Law of Motion

An easy activity that shows the law of physics at work is to play with marbles.  Ask each STEMist to choose two marbles and set one marble at the end of a flat surface.  Then, ask your STEMists to push the second marble into the first marble (at the end of the surface). Observe what happens when the two marbles collide—notice the reaction to the collision. Encourage your STEMists to talk about the transfer of energy from one marble to the next.  Also discuss that like the marble, any object hit with another would react to the action.

LEGO Balloon Car

LEGO car

A favorite teaching tool, LEGOs continually find their place in STEM-related activities! The LEGO balloon car activity will not only entertain your STEMists, it will demonstrate Newton’s 3rd law!  Ask your STEMists to build a car with LEGOs that includes an area on the back of the car to secure (between two LEGOs) the mouth of a balloon.  Add air to the balloon by inserting a straw in the balloon mouth, then blow into the straw.  Watch what happens when you release the straw from the balloon—as the air releases from the balloon, the car moves in the opposite direction.

If LEGOs are not available, you can design a paper rocket car that will demonstrate the same principle law of motion— for every force there is a reaction force that is equal in size, but opposite in direction.

Pop Tops

Pop top

Grab 2 film canisters, a seltzer tablet (Alka-Seltzer), water and a pan with sides (2.5 cm/1 inch or higher).  Use a permanent marker to draw a line down the center of the pan. Then, pour water into each canister until half full, and equal to each other.  Cap the first canister and lay it on its side with the cap facing toward the line on the pan.  Then, work quickly to add 1/2 of an Alka-Seltzer tablet to the second canister. Immediately cap the canister and lay it cap-side at the center line in the pan, facing the other canister.  Watch as the seltzer tablet creates enough gas to fill the canister and cause it to pop its top, and push against the first canister.  Your STEMists will witness equal force affecting each canister, causing them to move in opposite, mirrored direction.

Observe a Bird in Flight

Birds and Third Law of Motion

Take your STEMists outdoors to observe Newton’s 3rd law in action!  Watch a bird as it takes flight. Consider the flying motion of the bird and use of its wings as they push the air downwards.  The downward motion reacts to the opposite force of the air pushing the bird upwards. This makes perfect sense if your STEMists can remember that for every action, there is an equal (in size) and opposite (in direction) reaction – therefore, the action-reaction force makes it possible for the bird to fly.

For more ways to learn about science and physics, check out next month’s pulley-themed “Pull Your Weight” Groovy Lab in a Box.  Your STEMists will become engaged in the engineering design process as they work through investigations and the custom retro-style Groovy Lab notebook!