Describing and Measuring MOTION Section 1.1 Notes

Key Concepts When is an object in motion? How do you know an object’s speed and velocity? How can you graph motion?

Describing Motion You are in MOTION if your distance from another object is changing Depends on a REFERENCE POINT Place or object used for comparison

Describing Motion Are you moving? Reference point = SMARTboard Ref. pt. = Sun To determine motion, you must know your reference point!!

Relative Motion Motion is relative to your reference point. Questions: On the next slide, are the skydivers moving relative to each other? Are they moving relative to the airplane from which they jumped? Are they moving relative to the ground?

Relative Motion Boat example: people in boat compared to shore – why? people in boat compared to boat – why?

Measuring Distance You use units of measurement to describe motion SI System is used to describe the distance an object moves. Meter – basic measurement for length

Review: How many cm in a m? 100 centimeters in a meter How many mm in a m? 1000 millimeters in a meter How many m in a km? 1000 meters in a kilometer

Converting Units Practice Problem - Describing and Measuring Motion Converting Units Practice Problem How many centimeters are in 22.5 meters? HINT = Multiply length by 100. 22.5 m = 2,250 cm

SPEED The distance an object moves in a certain amount of time Speed = distance / time Units depend on measures of distance and time m/s km/h m/h

Average Speed Overall speed of an object Calculate by dividing total distance by total time

Instantaneous Speed Rate at which an object is moving at a given instant in time. Why is the instantaneous speed different from the average speed?

Question: Would a radar gun (used by police officers) measure average speed or instantaneous speed? WHY? Answer: Instantaneous speed

VELOCITY Speed in a given direction. You need to know the direction to know velocity Important to: pilots, weather forecasters, air traffic controllers

Graphing motion!! Motion graphs plot distance versus time Slope = rise/run Slope = distance/time Slope = speed of that segment

Graphing Motion

Converting Units - Describing and Measuring Motion Use a conversion factor to convert one metric unit to another. A conversion factor is a fraction in which the numerator and denominator represent equal amounts in different units. Multiply the number you want to convert by the conversion factor. Suppose you want to know how many millimeters (mm) are in 15.5 meters (m). Since there are 1,000 millimeters in 1 meter, the conversion factor is: 1,000 mm/1 m Multiply 14.5 meters by the conversion factor to find millimeters. 14.5 m X 1,000 mm/1 m = 14.5 X 1,000 mm = 14,500 mm

Graphing Motion Activity - Describing and Measuring Motion Graphing Motion Activity Cgp - 3011