motion. definition event that involves a change in the position or location of something
TRANSCRIPT
MotionMotion
Definition
Event that involves a change in the position or location of
something.
Motion is Relative
• Relative – it is described compared to a REFERENCE POINT
Types of Motion
• Uniform motion - constant speed in a straight line
• Accelerated motion – motion that is changing in speed or direction
• Circular motion - speed is constant but the direction of motion is changing continuously
Scalar Quantities
• Show magnitude [amount] only– Speed, time, temperature
Vector Quantities
• Show magnitude and direction– Velocity, acceleration, force
• May be graphically represented– Arrows
SpeedAverage Speed
• Comparison of time and distance– A scalar quantity [magnitude only]– Distance traveled per unit time
• S = d / tS = d / t
• T = d / sT = d / s
• D = s x tD = s x t
SpeedInstantaneous Speed
• Speed at any instant
SpeedConstant Speed
• Speed that does not change– Instantaneous speed that does not change
Velocity
• Speed AND direction– A vector quantity [magnitude & direction]
Acceleration
• A change in velocity– Speeding up
• Positive acceleration
– Slowing down• Negative acceleration• Deceleration
– Changing direction
Forces
• Pushes or pulls
• May cause acceleration [changes in motion]
• May also cause changes in shape
Balanced Forces
• All forces acting on an object are equal
• There is no motion
Unbalanced Forces
• All forces acting on an object are not equal
• One or more force is stronger than others
• Motion occurs
Net Force
• The sum of all forces acting on an object– A net force of 0
• No motion
– A net force of more than 0• Motion occurs
Resultant
• Another term for net force
Friction
• Force that slows down motion– Air resistance creates friction in most
situations
Gravity
• Force that attracts all objects toward each other
• More mass = more gravity
• Acceleration because of gravity is 9.8 m/s/s
• All objects accelerate at the same rate
Newton's Laws
• Describe motion and changes in motion
First Law of Motion
• Law of inertia– Objects at rest [not moving] will not begin to
move until a force acts on them– Objects in motion will not stop moving until a
force acts on them– Objects with more mass have more inertia
• Bigger objects are harder to start and stop
Second Law of Motion
• Law of acceleration– A force is needed to change motion– Objects accelerate in the direction of the force– The more force applied, then more
acceleration– The more mass an object has, the more force
is needed to accelerate the object
Third Law of Motion
• Law of action-reaction– Forces occur in pairs– The forces are equal and opposite– One force is an action force– The other force is a reaction force– The forces act on different objects