Motion in One Dimension Chapter Two Motion is

Motion in One Dimension Chapter Two

Motion is relative! n If you are traveling on a plane, you are not moving relative to the plane – you are moving relative to the Earth.

Motion is Relative! n n In physics, a frame of reference is chosen against which changes in position are measured. Commonly, the Earth is used as a frame of reference in physics problems, and motion is measured relative to Earth.

SPEED A measure of how fast an object is moving n Measured as a unit of distance divided by time n v = d/t n units: m/s (meters per second) n

INSTANTANEOUS SPEED n n n The speed at any given instant Example: Speedometer in a car Gives the speed of the car at an exact moment!

AVERAGE SPEED n Total distance covered divided by total time taken to cover that distance! n Does not give information about instantaneous speeds during that time interval!

Velocity Is not the same as speed – velocity is speed in a direction n 60 km/hr is speed n 60 km/hr North is velocity n Constant Velocity – no change in speed or direction! n Changing Velocity – change in speed or direction n

Velocity n What are three controls in your car that allow you to change velocity?

Velocity n GAS PEDAL

Velocity n BRAKE PEDAL

Velocity n STEERING WHEEL

Velocity n Always lots of fun! n What if velocity changes?

Acceleration Can be a change in speed or direction! n EXAMPLES: n Speeding up n Slowing Down n Changing Direction n

Acceleration There are two times when an object is not accelerating: n When it is stopped (not moving at all) n When it is moving at constant velocity. (if an object is moving at 10 m/s in a straight line, it has no acceleration!) n

Acceleration If an object is moving horizontally acceleration is shown by: Change in velocity Change in time If an object is slowing down, it has negative acceleration.

Acceleration n The Equation for acceleration is: n a = acceleration n v = velocity n t = time n Units: m/s 2 n a = v/t

Acceleration n Sometimes an object moving vertically experiences linear acceleration!

During Free-Fall n If an object is dropped or thrown and only gravity acts on the object after release, the object is said to be in a state of free-fall.

During Free-Fall Acceleration is constant during both upward and downward motion n Acceleration is always directed downward during free fall n