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. http://www.youtube.com/watch?v=

7gu1XDGSbe8 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