MotionChapter 1 in Motion, Forces, and Energy

To understand motion is to understand nature - Leonardo Da Vinci

Objectives of Ch. 1 Sect. 1

• Determine when an object is in motion.

• Calculate an object’s speed and velocity.

• Demonstrate how to graph motion.

Describing Motion Motion- if its distance from another

object is changing then an object is in motion

Reference point- a place or object used for comparison to determine if something is in motion

An object is in motion if it changes position relative to a reference point.

Stationary objects These are objects that make good

reference points.

Moving Reference PointsAre they reliable?

You are on Bus C looking at Bus D-oh my you are rolling backwards!!

Or are you?

Nope!!! As a matter of fact, you’re not moving at all!

But Bus D did move forward!

Did you choose a good reference point?

C

D

Relative Motion

Whether or not an object is in motion depends on the reference point you choose.

From the Plane

The plane does not appear to be moving.

The skydivers appear to be moving. The Ground appears to be moving.

Relative Motion From the Skydivers

The plane appears to be moving. The skydivers do not appear to be

moving. The ground is coming closer.

Relative Motion from the Ground

The plane appears to be moving.

The skydivers are coming closer.

The ground is not moving.

Measuring Distance

International System of Units (SI) To measure Use these units -Length -meter

-volume -liter -time -seconds -mass -kilogram

You try…..

How many centimeters are in 22.5 m? Convert 1.6km to meters. Convert 119cm to meters. Convert 6548 m to millimeters.

Calculating Speed

Speed= distance/ time s= d/t Possible units for speed are Kilometer per hour (km/hr) or Meter per seconds (m/s) *if you know the distance an object

travels in a certain amount of time, you can calculate the speed of the object.

Average Speed

Total distance divided by total time traveled

To find average speed. › Bike race with hills-Can you have a

constant speed?

Total distance =32km + 13km = 45kmTotal time = 2 hr + 1hr = 3 hrs

15 km/hr

Instantaneous Speed The rate at which an object is moving

at a given instant in time.

Velocity Speed in a given direction

Velocity is important to prevent collisions

Graphing Motion Time –x-axis (horizontal axis) Distance – y-axis (vertical axis) You can show the motion of an object

on a line graph in which you plot distance versus time.

A point on the line represents the distance an object has traveled at a particular time

Calculating Slope Slope-steepness of a line on a graph

Slope= rise/ run Slope represents speed since:

› Rise=distance /run=time

THE END OF THIS SECTION