Motion Chapter 1 book m

Describing and measuring motion Who can describe MOTION?  Motion : an object is in motion if its distance from another object or a reference point is changing.  So what does this mean?  How can you tell? Reference point: is a place or an object used for comparison to determine if something is in motion

Examples Walking away from the side of a building. Sitting in a chair that is being pulled? Lying on a bed on a train?

Relative motion Some of those examples depended on a relative point.  If you choose something close to you that is not moving when you are lying in bed then no but if you choose the buildings outside the train then you are.

Distance Measuring distance is using units to describe increasing or decreasing distances from motion mm, cm, m, km, in, feet, yard, mile, are all units of measuring distance.  What do we use so that everybody is on the same page? S.I.

Syst`eme International The International system of units  When we talk about measuring units and we need to communicate with other people around the world we all need to be on the same page. So they use the metric units of measure –The meter is the standard from which all other units come from.

Calculating speed How do we calculate speed?  If you know how long it takes an object to travel a certain distance. Then you can calculate speed.  The formula Speed = distance time Speed: unit of distance divided by a unit of time –Miles per hour feet per second

Average speed There are not very many things that have a constant speed. When driving a car the speed is always changing, diving in town vs. the freeway stop and go vs. open roads.  How do we find our average speed. You take the total distance traveled by the total time it took to travel that distance.

Examples. Say you ride the bus for a total of 15 miles and it takes you 60 min to get from your house to the school with all of the stops and traffic. What is the average speed?  What units would you use to describe the distance travled and the time it took.

Home work Tomorrow every body is going to figure out the average speed it takes them to get to school. WWhat do you need to know? Distance traveled Time it took. –I–If you ride the bus ask the driver what the miles are (to the nearest 10 th ) and time how long it takes you to get to school then ask what the miles are when you get here. We will do it in class and turn it in tomorrow

What is slow motion? Can you think of anything that is moving slow.  The planet moving  Flowers opening the speed of these things is relative They are moving much faster than we think you have to consider time and distance.

Acceleration Acceleration: is the rate at which velocity changes  What is velocity again? The speed and the direction of an object, to change velocity you can change speed, direction, or both.  In science acceleration refers to increasing speed, decreasing speed, or changing direction.

Increased speed Increasing speed: is when ever an objects speed increases.  Examples: a car speeding up, throwing a baseball, running downhill.

Decreasing speed Why do we call it acceleration when something is slowing down?  We call it negative acceleration, or deceleration when speed is lessened. Think about #’s a -2 is still a 2 just a negitive

Change in direction An object can accelerate even if the speed is constant.  How? Think of a car going around a curve, the car accelerates because the car changed direction. The simplest example of this type of motion is circular motion, the seats on a Ferris wheel accelerate because they move in a circle