Newton's 3 Laws of Motion!

ARE WE MOVING?

• When I think of moving, I just think of everyday movements that I and everyone else do. But is it true that we are always moving? What IS movement anyways??

• To start our understanding of Newton's 3 Laws of Motion, we did a lab with Hover Discs and drew interaction diagrams to further understand the different types of forces than can act on an object.

• When we turned on the Hover Discs, Newton's 1st Law of Motion was clearly demonstrated because it stayed at a constant speed unless a net force acted on it. We also did a Fan Cart Lab which is demonstrated in the picture below:

• We were already told that acceleration is a change in velocity over a change in time and that acceleration is the slop in a velocity vs time graph. 

• In this Fan Cart Lab, we were able to conclude that a net force is required to accelerate a massive object (Fnet=ma). This is also called Newton's 1st Law of Motion.

• We also concluded that the amount an object accelerates depends on the object's mass and the net force it experiences. In other words, if an object has a lot of mass, like a Hummer Limo, will require more force on it in order for it to accelerate in comparison to a feather, which will only require a very small amount of force in order to accelerate. This concept is also known as Newton's 2nd Law of Motion!

• Newton's 3rd Law of Motion is a little more tricky. Instead of explaining this law with the experiment that we did in class, let's look at a worksheet problem instead. In the situation below, a person is falling towards the Earth so the only force they have between them is gravitational force (Fg). The person is experiencing gravitational force in the downward direction towards Earth. The Earth is experiencing an EQUAL but OPPOSITE force because of the person. But how is this possible that the huge planet that we live on, and an individual's mass can have the same force acting on them? The reason this makes sense is because the Earth is SO massive, that it's ACCELERATION is very very very small. But once a human, in comparison to the Earth, has such a SMALL mass, his or her ACCELERATION is very very very big. 

• With all this talk of acceleration and force, it made me wonder about the initial question of this unit... ARE WE MOVING?

• Newton was able to prove that this concept of "movement" does not exist. He said that movement has to be measured with respect to something else. So when you get out of bed in the morning and walk down the hallway to brush your teeth, yes you are moving.. with respect to the shelves on your wall and to the floor you walk on and everything else in your house that remains still. 

• Going back to Newton's 1st Law of Motion, a force causes an object to ACCELERATE, not MOVE.

REAL WORLD EXAMPLE: Can we connect Newton's 3 Laws of Motion to Field Hockey?

1st Law of Motion: During a field hockey game, the ball starts in the middle of the field and depending on who has possession, one player will pass the ball to her teammate and then continue with gameplay. Before the whistle is blown and no one touches the ball, the ball remains in one place because there is no outside force exerted on it (except for gravity which is the reason it is on the ground and normal force because the ball is touching the Earth).

2nd Law of Motion: Once the whistle blows and the player passes the ball, the amount of force exerted on the ball by the player will determine how far the ball travels. Also, when players are fighting for the ball, there is usually a good ampount of body contact. Sometimes players run into eachother. The player with the larger amount of mass will experience a smaller acceleration during the collision of the two players while the player with a smaller mass might fall down or bounce off more. 

3rd Law of Motion: When these two players collide, they both will experience the same amount of force. Even though the less massive player fell over, it is just because the other player was more massive so experienced a smaller acceleration.