Let’s begin with some skydiving movies. Types of Forces Let’s begin with some skydiving movies. http://www.manifestmaster.com/video/

Gravity

Friction

Air Resistance ① Definition Air resistance is the FORCE that OPPOSES the motion of another object through the air.

Predict Observe Explain ② ③ ④ Your teacher (or a volunteer) is going to drop two pieces of paper: one piece of paper is flat and the other is crumpled up. Which piece of paper is going to hit the ground first? ② Predict ③ Observe ④ Explain

⑤ Draw arrows and label the force of gravity (Fg) and the force of air resistance (Far) Far Fg

⑥ Terminal Velocity Terminal velocity is the CONSTANT velocity (speed) that a falling object reaches when GRAVITY and AIR RESISTANCE are balanced.

⑦ The two forces acting on a skydiver jumping out of an airplane are GRAVITY and AIR RESISTANCE.     

⑧ Draw arrows and label the force of gravity (Fg) and the force of air resistance (Far). Far ANIMATION http://www.waowen.screaming.net/revision/force&motion/skydiver.htm Fg

How would skydiving be different on the Moon? Fg

⑨ The Moon has no ATMOSPHERE (no air). Therefore there is NO air resistance on the Moon.

⑩ Empty space (a place with no air) is called a VACUUM.

⑪ What will happen if a flat piece of paper and crumpled piece of paper are dropped at the same time on the Moon? Will one piece land first?

⑫ FREE FALL is the name given to objects falling that experience the force of gravity but no air resistance.   Simulation of Galileo’s free fall experiment...ignoring air resistance. http://www.visionlearning.com/library/flash_viewer.php?oid=1884

NORMAL FORCE ⑬ The symbol for NORMAL FORCE is FN Normal force is a force (usually a push) that is PERPENDICULAR to the surface of contact. The symbol for NORMAL FORCE is FN

Perpendicular means ⑭ AT RIGHT ANGLES or AT 90 DEGREES. DEFINITION: http://www.merriam-webster.com/dictionary/normal

Push against a wall. Draw an arrow and label the normal force ⑮ Push against a wall. Draw an arrow and label the normal force FN

The force a table exerts on a book. FN

⑯ Comparing normal force to friction: Friction force is PARALLEL to the contact surface. Normal force is PERPENDICULAR to the contact surface.

⑰ Tension Force The pull of a ROPE or STRING is called a TENSION force. The symbol for the force of tension is FT

⑱ Spring (Elastic) Force The pull or push of a SPRING, RUBBER BAND, or BOUNCY BALL is called SPRING FORCE. The symbol for the spring force is Fs

Now let’s try Identifying Interactions in Realistic Situations