standard physics - Unit 5

Newtons three laws of physics:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. 

II. The relationship between an object's mass m, its acceleration a, and the applied forceF is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.  

III. For every action there is an equal and opposite reaction. 

The first of Newtons laws rooted from Galileo's concept of inertia. This law is stating that an object in motion will continue to move, unless something (a force) is preventing it from doing so. 

     For example, if I were to push a binder across the table, technically it would keep moving if friction didn't exist. Or it could slide off the table and hit the ground where it would stay because of gravity. If it weren't for this law, you could never move an object without losing it forever. 

Basically, the second of Newtons laws is telling us that the acceleration of an object depends on the net force acting on the object and its mass. As the force (like friction or gravity) increases, the acceleration increases; as the mass of an object increases, the acceleration of an object decreases. 

    For example, if an object has a net force of 20N, and a mass of 4 kg, it's acceleration is 5 m/s^2.

Lastly, Newton's third law indicates that in every interaction between two objects, there is a pair of forces acting upon it. The sizes of the forces for each are equal and the direction of the forces are opposite. All you need to remember for this law is that forces always come in pairs and there is an equal and opposite action-reaction. 

     For example, think of a magnet. On a magnet, there is a positive force on one side, and a negative force on the other, meaning that the direction of the forces are opposite. We know that the two forces are equal because if there is nothing magnetic on a table, you can have the magnet facing up or down (positive or negative). If the forces weren't equal, one side would always be facing up. 

 This is the extent of my knowledge, hope it makes sense!