Motion!

Key Ideas An object in motion changes position. Speed measures how fast position changes. Acceleration measures how fast velocity changes.

Position Position = location of a place or object Reference Point = location to which you compare other locations You need a reference point to describe a location. Examples: Tyler is sitting next to Sarah. Santiago, Chile is about 3000km southwest of Brasilia, Brazil.

Latitude and Longitude

Distance May be straight-line length or length of a path or route Standard unit of measure is meters (m) Longer distances use kilometers (km) Shorter distances use centimeters (cm)

From Hickory to Holly Ridge Straight-line distance: 373 km (232 mi) Travel distance: (307 mi)

Motion Motion = a change in position over time A change in position is evidence that motion has happened

Relative Motion How you see an object’s motion depends on your own motion. 1XDGSbe8 1XDGSbe8 Which direction is the corvette moving in relation to the mustang? Which direction is the mustang moving in relation to the corvette?

Speed Speed = measure of how fast something moves, or the distance it moves in a given amount of time Greater the speed, faster object changes position Speed = distance/time, S = d/t Meters per second – m/s Kilometers per hour – km/h

Average Speed Speed is not constant Calculate speed over a specific distance Example = time each lap and add those times together, then average

Distance-Time Graphs Shows how distance and speed change over time Plots distance an object travels against the time

Velocity Velocity = speed in a certain direction Changes in direction or speed change velocity Examples: Does a car traveling west at 100 km/hr have the same velocity as a car traveling east at 100 km/hr? Does a car traveling east at 100 km/hr have the same velocity as a car traveling east at 75 km/hr?

Vector Vector = a quantity that has both size and direction Velocity is a vector because it has a size (speed) and a direction

Velocity vs. Speed Walking north from home to the store you travel at a speed of 5 km/h. Walking south back home from the store you travel at the same speed of 5 km/hr. Speed is still 5 km/hr But velocity is 0 km/hr because you ended up where you started!

Acceleration Acceleration = rate at which velocity changes

Types of Acceleration In same direction as motion Speeding up In opposite direction of motion Negative acceleration, slowing down At a right angle to motion Change direction but speed is the same

Formula for Acceleration

Velocity-Time Graph