Forces

Forces

1. A force is any influence that causes an object to undergo a specific change.

   • Thrust - increases the velocity of an object
   • Air resistance - decreases the velocity of an object
   • Torque - changes the direction of an object

2. Newton's First Law of Motion states that objects with balanced forces acting on them will stay at rest or in constant motion.

3. Newton discovered that objects will continue to do what they are doing until an unbalanced force acts on the object.

   • Forces act on objects
   • Forces cause changes

4. Newton's Second Law of Motion states that when an unbalanced force acts on an object...

   • ...the direction of the object's acceleration is the same as the direction of the unbalanced force.
   • ...the magnitude of the object's acceleration varies in direct proportion with the size of the unbalanced force.
   • ...the magnitude of the object's acceleration varies inversely with the mass of the object.

5. Friction is a force that opposes motion and is caused by two surfaces sliding past each other.

6. An object may have lots of forces acting upon it, and they are added together to create the resultant force.

   • If the resultant force is zero, a moving object will stay at the same speed.
   • If the resultant force is not zero, a moving object will speed up or slow down depending on the direction of the resultant force.