Force | Pushes and Pulls

Forces and Motion: Basics by Phet

Have you ever seen a Star Wars movie or heard people saying “they have the force”? The Star Wars franchise is famous for its use of the “force”, otherwise known as Jedi’s power to move things without touching them. But out of Star Wars, what is a force? It’s pretty simple, a force is a push or a pull. Really? That’s it? Well yes, and no. Forces may be as simple as a push and a pull, but Isaac Newton describes them as more. Newton has three famous laws that are used to determine forces. Number one, an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. But what does this look like. Take your pencil. Say you dropped your pencil off of the table. Your pencil stays in motion until it hits the floor and stops. You could argue that the floor is not a force, but is it? Right now, as you are standing, their are at least two forces acting upon you. Force number one, gravity. Gravity is currently pulling you down towards the earth’s center. This is what keeps you from floating around. Number two, the push of the floor. The floor is actually pushing you upwards. If it wasn’t, you would currently be sinking down into Earth’s core. This brings us back to your pencil, and Newton’s second law. This law states that F=MxA. Or Force equals Mass times Acceleration. Say that you pencil was the size of the desk you are dropping it off of. This would take a lot more push from the ground, or force, to keep this giant pencil from sinking into Earth’s surface. Which brings us to Newton’s third law. For every action, their is an equal and opposite reaction. Back to your pencil, when you drop your pencil it bounces back up a little bit. This is because of Newton’s third law. The action is your pencil dropping, the reaction is it coming back up and off of the ground in the opposite direction that you dropped it. There’s more to forces than Newton’s three laws.

Their is also a such thing as net forces. Net forces are the sum of all forces acting upon each axis. Things brings us back to you and the battle between the ground and gravity. The fact that you are not sinking into the ground, but not floating off to space is because the force of gravity and the force of the ground have a net force of 0. This is because each force is acting upon you with the same strength. The strength of a force is measured in Newtons or N. Back to your pencil, this time, your are sliding your pencil across the table to your friends. If you picture your pencil on a coordinate grid, it might help you. There are about 4 forces acting upon your pencil. Force one, gravity. For this problem, we will say that gravity has a strength of 150 N. Force two, the push of the table. We will say that it also has a strength of 150 N. Since these two forces are equal in strength and going in the opposite direction, they cancel each other out. This means that your pencil is neither moving up nor down. Force three, friction. The friction of the table is pulling your pencil back towards you, or in the opposite direction that the pencil is moving. We will say that it has a magnitude of 10 N left. Magnitude is the strength of the force as well as the direction. Force four, your push. Your push has a magnitude of 50 N right. Now to calculate the net force. The net force of the y-axis (as we figured out earlier) is 0. Now the net force on the x-axis. Since the two forces on the x-axis are going in opposite directions, we can assign the one going left the negative number. This would make the equation 50 N - 10 N. Then just subtract. The answer would be 40 N right, because that is the way that the pencil is moving. There is a lot to forces, but once you get the hang of it, it is pretty simple. A force is a push or a pull.

S&EP
SP8: Arguing from Evidence

Imagine this, hulk and the avengers are having a tug-o-war. Who do you think would win? I don’t have to imagine this. I argue from evidence when I said that the avengers would win because they are actually applying force, and a lot of it. Whereas, the Hulk is just standing there reading a book. Therefore, the avengers would win because they are actually trying. But not only do forces backup tug-o-wars, they also disprove double-jumping. Double-jumping, as I argued, is not possible. To leave the ground, you need the spring effect of you feet pushing down on the ground and the ground pushing up on you. As you probably know, the air does not push up on you, so for you to jump you would need some kind of solid force underneath you. Therefore, you can’t double-jump.

XCC
XCC: Stability and Change

Forces both stabilize thing and change them. When forces are balanced, they can stabilize things and hold them in place. Just like how the push of the earth and the pull of gravity keep you stable and on Earth’s surface. Or when the push of the table and the pull of gravity kept your pencil still on the table. But forces can also change things. Unbalanced forces cause things to change, especially in position and placing. Unbalanced forces is what causes objects to move and change their position. Like when you are rolling a ball, the ball was unmoving, balanced and stable, but your pushing was an unbalanced force that caused the ball to move, changing it’s position to another place. Forces are part of nature and are everywhere, you don’t have to look for when you want to see it.