Chapter 2—Motion and Force Section 1—Describing Motion Resource Science

Motion and Speed Motion—occurs when an object changes its position *Motion doesn’t always have to be seen to have taken place

Distance and Displacement Distance—describes how far something has moved SI base unit to measure distance is METER Displacement—the distance and direction of an object’s change in position from the starting point See figure 2 on pg. 39

Speed Speed-the distance an object travels per unit of time Ex: miles per hour/ feet per minute, etc. Rate—any change over time, so-- **Speed is a RATE Equation: Speed = Distance / Time (typically measured in m/s)

Practice Calculating Speed-pg. 42-# 1 and 2 *Most speeds aren’t constant, they either slow down or speed up Average speed-describes speed of motion when speed is changing (driving on a 3 hr. trip) Instantaneous Speed-speed at a given point in time Ex: speed on a speedometer

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

Remember: *To Calculate Velocity, it is the same as calculating speed, but you must also report a DIRECTION-north, south, east, west, etc. *One example of change in velocity—when a race car at a constant speed is rounding a curve, velocity is changing, due to direction of travel changing

Section 2—Acceleration Acceleration-the rate of change of velocity (velocity = speed w/direction) When the velocity of an object changes, the object is accelerating So: Acceleration occurs when an object changes its SPEED, its DIRECTION or BOTH

If speed is increasing = positive acceleration (acceleration) If speed is decreasing = negative acceleration (deceleration) Ex: horse on a carousel-acceleration due to direction only

Amusement Park Acceleration: Wooden and steel roller coaster provide different thrills due to different materials Wooden-swaying effect Steel-more loops, steep inclines, drops, etc.