NEWTON'S LAWS

==Newtons First Law== [image:http://i.imgur.com/jVJdHt4.png?1] An object will either remain at rest or continue to move at a '''constant velocity''', unless acted upon by an unbalanced force. An object floating in space will continue to move at a constant velocity unless a force is applied to slow it down. On earth most objects slow down (decelerate) because of resistive forces such as air resistance. If the forces applied to a moving object are balanced (net force is 0) the object will move at a '''constant velocity'''. If the object wasn't moving to begin with it will remain stationary (a constant velocity of 0). ===[image:http://i.imgur.com/to9h9k7.png?1]=== The vector arrows show that forces are balanced so the car continues to move at a constant speed. The size of the arrows represents the magnitude of the force. ==Newtons Second Law== An object will only '''accelerate''' (change its velocity) if there is a '''net''' or '''unbalanced force''' acting upon it. The acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. ===[image:http://i.imgur.com/ePH6IIr.png?1]=== The forces are unbalanced. There is a net force that causes the car to '''accelerate''' forward (to the left) if it started from rest. ===[image:http://i.imgur.com/jbHXa20.png?2]=== If the net force is acting in the opposite direction to the velocity of an object it will cause the object to decelerate (slow down). If you label the velocity as being in the positive direction, this can also be described as negative acceleration. ===Newtons second law can also be expressed using the following formula:=== [image:http://i.imgur.com/04yW9B6.png?1] [image:http://i.imgur.com/wDibmDk.png?1] '''''Note: Newton's Second Law actually states that a net force is equal to the rate of change of an object's momentum (F = dp/dt) but we can rearrange this expression into the familar form of F = ma.''''' ==Newton's Third Law== Whenever one body exerts a force on another, the second exerts an equal and opposite force on the first. These force pairs must be of the same type. [image:http://i.imgur.com/7NePVOP.png] This law applies to every force acting. A common saying is that '''"for every action, there is an equal and opposite reaction"'''. ===examples=== [image:https://i.imgur.com/Dh07ps4.jpg] [image:https://i.imgur.com/s1c3oox.jpg] [image:http://i.imgur.com/DAZja8b.png]