SPEED VELOCITY ACCELERATION SWBAT determine the speed velocity
SPEED, VELOCITY, & ACCELERATION SWBAT: determine the speed, velocity, and acceleration of moving objects
Motion : a definition • a change of position • flipping the pages of your notebook • earth revolving around the sun • any time you change your position—you are in motion
Relative Motion • Motion is RELATIVE • It is always described in relation to a reference point
Example • Earth rotates more than 1, 000 mph at the equator, but we can’t feel or see it spinning. Why? • Because everything we see around us is rotating at the same speed along with Earth. So, from our reference point nothing is moving #SCIENCE
• So pretty much, motion is simply relative to the observer. • but no, this will not get you out of a speeding ticket. Speed limits are for your car compared to the road you are driving on.
here is another example…. or two • Tailwinds—the speedometer on a plane may say that plane is going 100 km/hr, because that is how much power the motor is putting out to make the plane go that fast—but tailwinds can speed it up by pushing the plane to go faster, so compared to a person on the ground, with a tailwind of 20 km/hr, the plane is actually going 120 km/hr. • Headwinds—same concept, but these push against the plane and so where the plane’s speedometer reads 100 km/hr—a 20 km/hr headwind will slow the plane down to a speed of 80 km/hr compared to a person on the ground.
How do we calculate motion? • Speed : the distance { something travels in a certain amount of time àSI units: àdistance measured in METERS (m) àtime measured in SECONDS (s) Speed = change in distance change in time } Example: The average NFL quarterback can throw a football at a speed of 50 mph. This means that it would only take a football an hour to travel 50 miles! Impressive.
What does speed not describe? DIRECTION Sometimes it is also important to know the direction an object is moving.
Velocity = Speed + Direction Speed with direction is called velocity. • velocity is a vector quantity (what does this mean? ) • words used to describe direction: north, south, east, west, up, down, left, right, etc. • an object with constant velocity has both constant speed and constant direction 60 mph north
Velocity average velocity = displacement / time Remember to include a direction!
Guided Practice Deonte’ is out in the woods hunting a turkey for Thanksgiving. He spots a turkey walking around at a brisk pace. It covers 50 ft in 10 seconds! What is the turkey’s walking speed?
Guided Practice David is out in the woods hunting a turkey for Thanksgiving. He spots a turkey walking around at a brisk pace. It covers 50 ft in 10 seconds! What is the turkey’s walking speed? What formula? David glances at his compass and sees the turkey is walking north. What is the turkey’s velocity?
Guided Practice: Solving Word Problems The longest stretch of railroad tracks lies across the desolate Nullarbor Plain, between the Australian cities of Adelaide and Perth. The track extends 478 kilometers without a curve. How long would it take a train moving at a constant speed of 97 km/hr to travel the length of this track?
Guided Practice: Solving Word Problems The longest stretch of railroad tracks lies across the desolate Nullarbor Plain, between the Australian cities of Adelaide and Perth. The track extends 478 kilometers without a curve. How long would it take a train moving at a constant speed of 97 km/hr to travel the length of this track? How do I solve this?
Guided Practice: Solving Word Problems The longest stretch of railroad tracks lies across the desolate Nullarbor Plain, between the Australian cities of Adelaide and Perth. The track extends 478 kilometers without a curve. How long would it take a train moving at a constant speed of 97 km/hr to travel the length of this track? What values do we know? Step 1: Circle, label, distance: and write down any known values. Identify the unknown(s) and choose variables to represent them. time: speed:
Guided Practice: Solving Word Problems The longest stretch of railroad tracks lies across the desolate Nullarbor Plain, between the Australian cities of Adelaide and Perth. The track extends 478 kilometers without a curve. How long would it take a train moving at a constant speed of 97 km/hr to travel the length of this track? Step 2: Determine What values do we know? what equation to use. distance: time: speed:
Guided Practice: Solving Word Problems The longest stretch of railroad tracks lies across the desolate Nullarbor Plain, between the Australian cities of Adelaide and Perth. The track extends 478 kilometers without a curve. How long would it take a train moving at a constant speed of 97 km/hr to travel the length of this track? What values do we know? distance: time: speed: Step 3: Solve for the unknown.
Guided Practice: Solving Word Problems The longest stretch of railroad tracks lies across the desolate Nullarbor Plain, between the Australian cities of Adelaide and Perth. The track extends 500 kilometers without a curve. How long would it take a train moving at a constant speed of 100 km/hr to travel the length of this track? What values do we know? distance: time: speed:
Guided Practice The fastest supersonic passenger jet is the Concorde. How long would it take Concorde to travel the 6265 km between New York City and London, England, assuming that the jet travels at its maximum speed of 2150 km/h during the entire trip? What values do we know? distance: time: speed: Step 1: Circle, label, and write down any known values. Identify the unknown(s) and choose variables to represent them.
Guided Practice The fastest supersonic passenger jet is the Concorde. How long would it take Concorde to travel the 6265 km between New York City and London, England, assuming that the jet travels at its maximum speed of 2150 km/h during the entire trip? What values do we know? distance: time: speed: Step 2: Determine what equation to use.
Guided Practice The fastest supersonic passenger jet is the Concorde. How long would it take Concorde to travel the 6265 km between New York City and London, England, assuming that the jet travels at its maximum speed of 2150 km/h during the entire trip? What values do we know? distance: time: speed: Step 3: Solve for the unknown.
Acceleration • The rate at which velocity changes with time is called ACCELERATION. • When an object changes velocity, it is accelerating. It does this by: SPEEDING UP SLOWING DOWN CHANGING DIRECTION
Formula: { } final velocity – initial velocity acceleration = time Measured in units of METERS PER SECOND SQUARED (m/s 2 )
• Because velocity takes direction into account, so does acceleration. • So, when your car goes around a corner, you feel acceleration when you feel pushed towards the ouside of the car. • (This is also why the bigger person has to sit on the outside in a fair ride)
Acceleration Decelerator • Positive when it is in the • Negative when it is in the same direction as the object’s motion. • “Speeding up” --what do you use to speed up in your car? opposite direction of the object’s motion • “Slowing down” --what do you use to slow down your car?
Check Your Understanding 1. What is the formula for 3. Why do we refer to speed? motion as relative? 2. A dolphin swims 56 4. What is required to meters in 8 seconds and know the velocity of an a walrus swims 30 object? meters in 6 seconds. Which is faster?
Check Your Understanding 5. If you walk around a square block going the same pace, how many times does your velocity change? Your speed? 6. If a truck drives 30 km/hr one direction and then turns and goes the other direction at 30 km/hr. What changes, the speed or velocity? 7. If a bee is flying in a circle at a constant speed, is the bee accelerating? 8. What are three ways something can accelerate?
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