SNB page 41 Underline= Highlight Red= Don’t write

 Unbalanced forces cause acceleration. Without the upward normal force exerted by the table, the ball accelerates downward because of the unbalanced force of gravity. 2.3 Unbalanced Forces and Acceleration

 Unbalanced forces cause an object to accelerate.  The acceleration of an object equals the net force divided by the object ’ s mass. a = F/m or F = m  a

 An object’s speed will increase when a net force acts in the same direction as the object’s motion.

 What will happen to an objects speed when a net force acts in the same direction as the object’s motion? 1) It will not move (balanced force) 2) It will speed up 3) It will slow down 4) It will change direction

 An object’s speed will decrease when a net force acts in the opposite direction of the object’s motion.  Friction is applied in the opposite direction and slows the sled down.

 What will happen to an object when a force is applied in the opposite direction that the object is traveling? a) It will not move (balanced force) b) It will speed up c) It will slow down d) It will change direction

 Unbalanced forces can also change the direction of motion.  A thrown ball curves downward because of the unbalanced force of gravity.

 You toss your friend a football and it curves downward is an example of an object: a) Not moving (balanced force) b) Speeding up c) slowing down d) changing direction

 Centripetal force is the force that keeps an object moving in a circle. A ball tied to a string and swung is a horizontal circle has circular motion. The velocity of the ball changes because the direction of motion changes. The string exerts an unbalanced force on the ball called centripetal force.

In what direction does the net force of an object moving with constant speed and in a circular motion occur? 1downward 2opposite to the object’s motion 3toward the center of the circle 4in the direction of the object’s velocity FINGER RESPONSE

 List the following examples of a “balanced force” or “unbalanced force” 1) A driver speeds up to get onto the freeway. 2) The driver continues to drive 70 mph 3) The driver uses her brakes to slow down because of traffic.

1. Net Force and Acceleration Worksheet ◦ SNB pg Ch 2.2 RSG

SNB page 43 Blue = Highlight Orange = Don’t write

 Unbalanced forces cause an object to accelerate.  The acceleration of an object equals the net force divided by the object ’ s mass. F = m  a

Acceleration depends on both the force applied and ____. 1distance from the object 2speed of the object 3mass of the object 4normal force of the object FINGER RESPONSE

 If the net force is equal to zero, the forces are balanced, the acceleration is zero and the object ’ s motion does not change.

How does the motion of an object traveling in a straight line at 5 m/s change if a balanced force is applied? 1The motion does not change. 2The object speeds up. 3The object slows down. 4The object travels in a horizontal circle. FINGER RESPONSE

 According the Newton ’ s second law, there must be an unbalanced force acting on Earth and the other planets. The Sun ’ s gravity is the centripetal force that keeps Earth and the planets moving in a circular path around the Sun.

 When one object exerts a force on another, the second object exerts an equal force in the opposite direction. The feet exert a force on the ground and the ground exerts an equal force on the feet of the jumper, causing the jumper to accelerate upward. Newton ’ s Laws of Motion Part APart A Part BPart B

When one object exerts a force on another object, what does the second object do? 1The motion does not change. 2It exerts an equal force in the same direction 3It exerts an equal force in the opposite direction 4The object travels in a horizontal circle. FINGER RESPONSE

 The forces that two objects exert on each other are called force pairs. The pairs are opposite in direction with equal in magnitude. The forces do not cancel out because they act on different objects.

 One force in a force pair is called the action force. The second force in a force pair is called the reaction force. For every action force there is an opposite and equal reaction force.

 List the following Newton’s “second” or “third” law of motion. 1) F = m  a 2) If the acceleration is zero and the object ’ s motion does not change. 3) For every action, there is an equal and opposite reaction

 Follow Mr. Klimenko’s instructions to fold the paper.  Label the front as: ◦ Newton’s First Law of Motion ◦ Newton’s Second Law of Motion ◦ Newton’s Third Law of Motion  Write your name, date and period on the back.  On the back of the tab, write the definition.  Behind the tab, draw or write an example.