Chapter 10: Motion

Observing Motion Reference point: stationary object from which motion is observed Motion involves distance, time and direction Displacement measures the change in position or the straight-line distance traveled by an object

Measuring Motion Speed: –how fast an object is moving –distance/time Velocity: speed with direction v= d/t d=vtt=d/v Speed can be determined by a distance vs. time graph distance vs. time graphdistance vs. time graph Instantaneous speed and average speed Instantaneous speed and average speed Resultant velocity Resultant velocity

Section 2 Acceleration Acceleration Change in velocity Can be change in speed or Change in direction Uniform circular motion is constant acceleration

Calculating Acceleration Rate at which velocity changes: Acceleration= final velocity – initial v time a=v f -v i t Units are m/s/s or m/s 2

Related equations t= v f -v i a v f = at+v i v i = v f -at Falling objects: v f =at

Graphs

Section 3: Motion and Force A force is a push or a pull A net force is the combination of forces acting on an object Balanced forces produce no net force and do not change the motion of an object Unbalanced forces do not cancel out and then cause a change in motion

Friction A force that opposes motion between two surfaces that are in contact Static friction is a stationary force Kinetic friction opposes the movement of two surfaces –Types and examples of kinetic friction: Types Rolling Sliding Fluid

Reducing harmful friction Reducing harmful friction Use of lubricants Replacing sliding friction with rolling Make surfaces smoother Reduce surface area Examples:

Increasing helpful friction Make surfaces rougher Increase surface area Adding to the forces of the objects in contact (adding weight) Examples: