Section 2-1: What is a force?

Forces acting on objects Force is simply a push or pull on an object It has both size (a number) and direction Express force in a unit called a Newton (N)

Acting on objects All forces act on objects Does not mean that motion will occur Sources and receivers of forces You cannot see all sources and receivers of forces: For example: Magnet’s force on a refrigerator Air held near Earth by gravity

Determining net force Net force = the combination of all forces acting on an object Usually there is more than one force acting on an object

Forces in the same direction When forces act in the same direction, you add the forces to determine net force Mrs. Bannon 20 Newtons Net force = Mr. Mager 30 Newtons 10 Newtons

Forces in opposite directions When forces act in opposite directions, you subtract the forces to find net force Net force acts in the direction of the larger force 20 newtons east 10 newtons west Net force = 10 newtons east

Balanced forces When forces acting on an object produce a net force of o newtons Will NOT cause a change in motion 10 newtons east 10 newtons west

Unbalanced forces When forces acting on an object produce a net force that is not 0 newtons 20 newtons east 10 newtons west What is the net force?

Unbalanced forces continued Will cause a change in motion An object can continue to move, even after the unbalanced forces are removed from the object

Forces practice- Push or a pull 1. 2. 3. 4. 5.

Forces practice 1 Look at the following picture. Choose the best answer to complete each sentence and write the answer on your board (You do NOT have to write the entire sentence).

Practice 1 The forces shown are PUSHING/ PULLING The forces shown are WORKING TOGETHER/ OPPOSITE FORCES The forces are EQUAL/ NOT EQUAL The forces DO/ DO NOT balance each other The resultant force is 1000N TO THE RIGHT/ 1000 N TO THE LEFT/ ZERO There IS/ IS NO motion.

Forces practice 2 Look at the following picture. Choose the best answer to complete each sentence and write the answer on your board (You do NOT have to write the entire sentence).

Practice 2 The forces shown are PUSHING/ PULLING The forces shown are WORKING TOGETHER/ OPPOSITE FORCES The forces are EQUAL/ NOT EQUAL The forces DO/ DO NOT balance each other The stronger force is pulling to the RIGHT/ LEFT The weaker force is pulling to the RIGHT/ LEFT Motion is to the RIGHT / LEFT