th 8 ScienceMotion Speed Acceleration Motion and Speed

th 8 Science-Motion, Speed, Acceleration

Motion and Speed • Position-the location of an object • Motion—occurs when an object changes its position • *Motion doesn’t always have to be seen for a motion to have taken place • Reference Point-used to determine how far something moves – Ex: mailbox while driving, etc.

Distance and Displacement • Distance—describes how far something has moved – SI base unit to measure distance ismeter – Displacement—the distance and direction of an object’s change in position from the starting point (how far you are from where you started)pg. 175

Speed • Speed-the distance an object travels per unit of time – Ex: miles per hour/ feet per minute, etc. – Rate—any change over time – **Speed is a rate – Equation: Speed = Distance / Time – typically measured in m/s but could be km/hr or mph, etc.

• Most speeds are not constant, they either slow down or speed up • Average speed-describes speed of motion when speed is changing-(total distance / total time) • Instantaneous Speed-speed at a given point in time – Ex: speed on an odometer in car • *pg. 177 -distance/time graph

Velocity • Velocity--includes the speed of an object AND the direction of its motion • *Velocity can change even if speed remains constant • Change in Velocity—can be EITHER a change in speed OR in direction of movement • *Graph-pg. 179 -complete

Plate Tectonics • The motion of the Earth’s crust creates the continental drifting that occurs every year • Plate Tectonics Theory-Pangea • Plates move so slowly that their speeds are given in units of centimeters per year. • Australian plate-1 of fastest—moves Australia north at an average speed of 17 cm. /year