A simple demonstration of Newton's 3rd law of motion in action. A rubber band under tension is cut, launching both the sled and the launching mechanism in equal and opposite directions.
This is a fun and easy demo to teach what happens to objects when forces are acting in the same direction. A series of balls are dropped together, one on top of another. The forces are added together, creating a larger force that propels the top ball to a much greater height.
I bought this fire syringe from the Science Outlet. The video above shows that when the piston is forced down rapidly, the air molecules compress causing a huge increase in temperature. This causes the piece of cotton in the syringe to ignite. This is very similar to what happens with the reentry of the space shuttle into the Earth's atmosphere.
Inertia is the tendency of an object to resist a change in its motion. An apple and a knife are moving downward. The counter-top applies an unbalanced force upward on the knife. The knife decelerates, but the apple does not. The apple decelerates only when the knife handle applies a force upward on it.
According to Newton's first law of motion, an object moving at constant velocity will continue to move at constant velocity unless an outside unbalanced force is applied. This is why moving objects on Earth will always slow down and stop. The outside unbalanced force that does it is friction. Watch the video to see how friction affects the motion of a marble on a track.