Force & Motion What are forces in your everyday life that are acting on us, but we do not notice them? 1. Take out your lab from yesterday.

Warm-Up Take out a sheet of paper. Write out question below and in your own words explain how you would solve it. Question: A student is kicking a soccer ball with a force of 120N in an upward direction and air resistance acting on the ball is 12N. What is the net force?

Motion A change in the position of an object Caused by force (a push or pull)

Force A push or pull on an object Measured in units called Newtons (N) Measured with a spring scale Forces act in pairs Key Types of Force: Gravity-a force that attracts two objects Friction-a force that slows or stops the motion of the object Air Resistance

Balanced Forces When all the forces acting on an object are equal (net force is zero) Balanced forces do not cause a change in motion. Examples- Object at rest stays at rest. Object in motion continues moving at a constant rate. A box is not moving as two students push it towards one another with equal force. 

Unbalanced Forces When all the forces acting on an object are not equal The forces can be in the same or opposite directions. Unbalanced forces cause a change in motion. Example: Object speeds up Objects slows down Applying the brakes causes a moving car to stop

How Can Unbalanced Forces Affect Objects? Acceleration is caused by unbalanced forces—It is any change in an object’s motion. Examples: Start, Speed Up, Slow Down, Stop, Change Direction

Net Force The total of all forces acting on an object: Forces in the same direction are added. The object will move in the direction of the force. Forces in opposite directions are subtracted. An object will move in the direction of the greater force.

Calculating Net Force 10 N 30 N http://commons.wikimedia.org/wiki/File:Jack-in-the-box.jpg A child was playing with a jack in the box. The lid pushed down with 10 N of force, while the spring pushed up with 30 N of force. What is the net force applied by the spring?

Calculating Net Force Two competitors are playing tug of war. Tug of War Game 30 N 50 N Two competitors are playing tug of war. What is the net force? Which direction will the rope move?

40 N 60 N

10 N 10 N