4.  How do you know an object is moving?  An object is moving if its position changes against some background that stays the same.

5.  The stationary background is called the reference frame.  The change in position is measured by the distance traveled by an object from a fixed point.

6.  Speed describes how fast an object moves.  Speed is measured by calculating the distance traveled by the time.  SI units meters per second (m/s)

7.  Speed can also be measured in Kilometers per hour (km/h) and miles per hour (mi/h)  Constant speed is the simplest type of motion.

8.  An object is moving at a constant speed when it covers equal distances in equal amounts of time

9.  Speed can be determined from a distance-time graph  Time is given on the X axis  Distance is given on the Y axis  Speed can be determined by calculating the slope of the line

10.  Speed = Distance Time V = d/t http://www.youtube.com/watch?v=DRb5PSxJerM

11.  Velocity describes both speed & direction of the motion  Example: The car was traveling at 50 mi/h headed north

12.  The velocity of an object changes if its speed or direction changes.  Does a car’s velocity change when it turns a corner?

13.  Which is harder to stop…  A speeding train or a speeding bicycle?  A grown man or a small child  Stampede of elephants or a stampede of mice?  Why?

14.  Momentum is a quantity defined as the product of an object’s mass and its velocity  Moving objects have momentum

15.  If an object is moving in a straight line, momentum is calculated by multiplying an object’s mass by the velocity

16.  An object’s momentum is in the same direction as its velocity.  Measured in kilograms X meters per second  kg X m/s

17.  Momentum = mass X velocity P =mv

18.  The total amount of momentum in a system is conserved

19.  A 135 kg speed racer moving forward at 16m/s  A 25 kg ostrich running north at 16.2 m/s  A 48.5kg passenger on a train stopped on the tracks

21.  Acceleration is the change in velocity divided by the time

22.  Acceleration = Final velocity – Initial velocity Time If the acceleration is small, the speed in increasing gradually. If the acceleration is large, the speed is increasing rapidly.

23.  Positive acceleration means the object’s velocity will __________.(speed up)  Negative acceleration means the object’s velocity will decrease (slow down) Increase

24.  A flowerpot falls off a second-story windowsill. The flowerpot starts from rest & hits the sidewalk 1.5s later with a velocity of 14.7 m/s.  What is the average acceleration?

25.  Acceleration can be determined from a velocity-time graph.  What information is on the X axis?  What information is on the Y axis?  The Acceleration of an object is O if its velocity is constant Why?

26.  Force is the cause of acceleration, or change in an object’s velocity.

27.  Many forces can act on an object at a given time.  Net Force is the combination of all the forces acting on an object  They determine whether the velocity of an object will change

28.  An object’s acceleration is in the direction of the net force.  Objects will not accelerate if the net force is zero.  Balanced forces do not change motion

30.  Balanced forces are forces acting on an object that combine to produce a net force equal to zero  The forces “cancel” each other out.

31.  Will produce a net nonzero force.  If there are unbalanced forces in different directions they will act like a single force on the object.  The net force will cause the object to accelerate

32.  Friction is the force between 2 objects in contact that opposes the motion of either object.  Example: The forces to move a car forward must be unbalanced.  The force moving forward must be greater than the friction opposing the car’s motion.

34.  Example:  Tennis shoes on a waxed floor versus shoes with very little tread.  (Someone is going to fall)

35.  Air resistance opposes the motion of an object.  Air Resistance is caused by the interaction between the surface of the object & the surrounding air molecules  Depends on the object’s size & shape

37. Key Vocabulary:  Speed  Velocity  Momentum  Acceleration  Force Unbalanced Forces Balanced Forces Inertia Gravity Friction

38.  Gravity is the attraction between 2 particles of matter due to their mass.  The force of gravity will act on objects that do not touch.  Mass & distance affect gravitational force

39.  The greater the mass of an object, the larger the gravitational force it is exerts on other objects.  Earth’s gravitational force is very large due to Earth’s massive size.  What would happen if the force wasn’t as strong?

40.  The force of gravity changes as the distance between two objects changes.  Gravitational force between two object will ____________as the distance between 2 object increases.

41. Newton’s Laws of Motion!

43.  An object at rest remains at rest & an object in motion maintains its velocity unless it experiences an unbalanced force.

44.  Compare sliding your book across carpet & ice…  On which surface will it slide longer?  Why?  Smooth surfaces provide less friction to oppose motion.

45.  Inertia is the tendency of an object to remain at rest or in motion with a constant velocity.  All object have inertia because they resist changes in motion.  The greater the mass of an object, the greater the force that has to be applied to cause the object to move.

46.  The unbalanced force acting on an object equals the object’s mass times its acceleration.

47.  Force = mass x acceleration  Example:  Pushing an empty shopping cart vs. pushing a really full one. Which one would need more force?

48.  Acceleration will occur in the direction of the net force.  Force is measured in Newtons  1N = 1kg X m/s 2 1N = 1kg X m/s 2

49.  Mass = 175 kg  Acceleration =.657m/s 2  What is the force?  115N

50.  When the force of gravity is the only force acting on an object it is said to be in free-fall.  The free-fall acceleration of an object is directed toward the center of the Earth.  g= 9.8 m/s 2

51.  Free-fall acceleration near Earth’s surface is constant.  In the absence of air resistance, all objects near Earth’s surface accelerate at the same rate regardless of their mass.  9.8m/s 2

52.  The force on an object due to gravity is called Weight.  Weight = mass x free-fall acceleration  w=mg  (g = free-fall acceleration)

53.  The SI unit for weight is the Newton  Weight is the gravitational force on an object due to its mass.  Weight influences shape (structure)  Example: Skeletons in elephants

54.  Velocity is constant when air resistance balances weight  For a falling object, when the force of air resistance becomes equal to the gravitational force on the object it stops accelerating & reaches Terminal Velocity

55.  For every action force, there is an equal and opposite reaction force.  “The law of action & reaction”  Forces always occur in pairs