 Changes in motion can be measured and graphically represented.  Forces cause changes in position, speed, and direction.

 Motion is a change in position, which is measured by distance and time.  Anything moving is in motion.

 A force is a push or pull that can change motion.  A force can move an object.  A force can transfer energy to an object.  For example, pushing on a wall doesn’t move the wall, but energy is being transferred.  Force = mass x acceleration

 In order for a force to move an object, there must be unbalanced forces.  Like tug of war…the winners are pulling the other team with more force; therefore, the pulling forces are unbalanced. wiki/File:Tug_of_war_2.jpg

 Unbalanced forces can change the position, speed, or direction of an object.  Resistance forces (friction or wind) that oppose motion can slow down an object.  A force in the same direction can cause an object to speed up.  A force from a different direction can change the object’s direction.

 If we have unbalanced forces, then there must be balanced forces.  When forces are balanced, an object’s motion will be constant. It will not change speed or direction.

 We talk about speed everyday.  Speed is the distance traveled by a moving object per unit of time.  Speed affects the energy of an object. The faster it moves, the more kinetic energy it has.  Speed = distance time

 The energy of motion  Objects in motion have kinetic energy.  Speed and mass affect the kinetic energy of an object.  If two objects are moving at the same speed, but one object has a greater mass—then the object with the greater mass will have more kinetic energy.  The more mass in an object, the more force needed to move it.

 If I traveled 30 meters in 10 seconds, what was my speed? o S = D/T o 30m/10s o 3 m/s

 Distance is a description of how far an object traveled between two points.

 Velocity and speed are like fraternal twins- very similar, but with important differences.  Velocity is speed in a given direction.  35 mph NORTH  4 km/sec EAST

 100 m/s right  1500 km/s  65 m/s north  3000 km/s Velocity Speed Velocity Speed

 Acceleration is a change in the rate of speed.  It can be a change in speed, direction, or both.  Acceleration = Change in speed (m/s) Time (s)  Example: 0 to 60mph in 3s

The race car accelerated from stop to 60 m/s by the finish line. It took the race car 8.0 seconds to finish. What was the acceleration? Original speed = 0 Final speed = 60 m/s Time = 8.0 seconds Acceleration = m/s = 7.5 m/s 2 8.0s

 Friction is a force that opposes motion.  It can be caused by wind, water, surface texture, etc.  Have you ever ridden down the street on your bike and felt the wind push against you?  That’s air resistance!  Air resistance is the frictional force from the air that resists forward motion.