9.2 Essential Question: How Do Objects React to Forces? Balanced & Unbalanced Forces How Do Forces Affect Motion Pgs. 336-339

Pearson Interactive Video

The net force determines if an object will move or accelerate. Vocabulary 9.2 Net force- The combination of all the forces on an object. The net force determines if an object will move or accelerate.

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How Do Forces Affect Motion? Often more than one force acts on an object at the same time. The combination of all the forces on an object is called the net force. It determines if and how an object will accelerate. If all the forces acting on an object are balanced, the object’s motion will not change. When the sum of all forces acting on an object is unbalanced, the object’s motion will change.

How do forces affect motion? Pg. 337 If all the forces acting on an object are ____________, the object’s motion will ____change. When the sum of all forces acting on an object is _________, the object’s motion will __________.

Balanced and Unbalanced Forces Net Force The change in motion of an object is determined by the net force acting on the object. What is the net force for each situation?

How to find the NF of an object You can find the net force on an object by adding together the strengths of all the individual forces on the object. When the total is a nonzero number (not zero), the forces are said to be unbalanced. When the total is 0, the forces are balanced. Balanced forces do not change the motion of an object.

2nd Law of Motion If two dogs are on each side, then the total force pulling to the left (200 N) balances the total force pulling to the right (200 N). That means the net force on the sled is zero, so the sled doesn’t move.

Balanced and Unbalanced Forces pg. 338 Which of these three arrows below represents the correct amount of net force of the above two force arrows?

How do forces affect Motion? When forces on an object act in opposite directions, you find the strength of the net force by subtracting the strength of the smaller force from the strength of the larger force. This net force is in the same direction as the larger force.

Acceleration = Net Force Mass