Newton's Laws and the Winter Olympics, Part 3

After a fun discussion about Newton’s 2nd Law and the Winter Olympics, it’s time to talk about Law #3! Newton’s 3rd Law of Motion is one of my favorites and also one that is often misunderstood.

Newton’s 3rd Law is often summarized as “For every action, there is an equal and opposite reaction”. I like to think about as “forces come in pairs”. It’s not about cause-and-effect or a sequence of forces. It’s about pairs of forces occurring at the same time.

For example, let’s say I’m at a roller skating rink on a field trip with my class. I’m standing near the wall, on roller skates. I push against the wall really hard. At the same time, the wall is pushing equally hard against me, in the opposite direction, so I roll backwards. The pair of forces includes my pushing against the wall and the wall pushing against me, but since the wall is secured to the floor, but I am not, I will roll backwards. And hopefully not fall over.

That example also applies to any sport in which athletes are pushing against something to propel themselves in any direction! In the Winter Olympics, Newton’s 3rd Law applies to:

• Skating: Whether speed skating or figure skating (or even hockey), skaters need to move. Often, they do this by pushing skates against the ice, which means the ice will be pushing their skates (and subsequently, them) in the opposite direction.

• Ski Jumping: When a ski jumper is ready to jump from the bottom of the ramp, they will push down against the ramp with their skis - which also means the ramp is pushing against their skis in the opposite direction (up).

• Biathlon: A rifle (or other firearm) is a classic example of Newton’s 3rd Law. When the bullet is pushed forward (usually very, very hard), the bullet also pushes backwards on the weapon, causing the weapon to fling backwards into the shooter’s face (called recoil). This makes it harder for the shooter to fire accurately again.

When do you notice Newton’s 3rd Law?