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Understanding Motion. Brittany Moore 8/29/12. What is motion?. motion : movement What two things are important in describing motion: Distance Time Do you have to see something literally move to know its in motion?. Distance vs. Displacement. Distance : how far something has moved - PowerPoint PPT Presentation
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Brittany Moore8/29/12
Understanding Motion
motion: movement
What two things are important in describing motion:DistanceTime
Do you have to see something literally move to know its in motion?
What is motion?
Distance: how far something has movedMeters (m), kilometers (km)
Displacement: distance and direction of an object’s change in position from the starting point
What are the differences between distance and displacement?
Distance vs. Displacement
Speed: distance an object travels per unit of timeHow do we calculate speed?
Speed = distance/time
Ex: A car traveling at a constant speed covers a distance of 750 m in 25 s. What is the cars speed?
Speed
A passenger elevator travels from the first floor to the 60th floor, a distance of 210 m, in 35 s. What is the elevators speed?
A motorcycle is moving at a constant speed of 40km/h. How long does it take the motorcycle to travel a distance of 10km?
More examples of speed
Does your car always run at a constant speed?
What might a graph of your car’s speed look like on a typical day to school?
Can speed change over time?
Average speed: total distance traveled divided by the total time of travelEx: A runner travels 100 m in 30 s. What is
their average speed?
Instantaneous speed: speed at a given point of timeEx: On my way to school I look down to see
that I am travelling 136.8 km!
Types of Speed
What kind of graph would be best to show motion? Distance over an amount of time…
How does the steepness of a line effect the speed?Speed = slope
How are graphs used?
Example
Lets have a race…can you calculate your speed?Speed = distance / time = m / s
Work in groups to complete worksheet.
Yay for Outside!
Velocity: speed of an object and the direction of its motion
The velocity of an object can change even if the speed of the object stays the sameEx: BMS—the race car has a constant speed
and is going around an oval track; even though the speed remains constant, the velocity changes because the direction of the car’s motion is changing constantly
Velocity
Example
Acceleration: the rate of change of velocityAcceleration occurs when an object changes its speed,
direction, or both.
Change in velocity = final velocity – initial velocityAcceleration = Vf – Vi Units in m/s
2
tEx: Speeding up and slowing down.
As a car speeds up: positive velocity, acceleration, and speed.
As a car brakes: positive velocity, negative acceleration (deceleration) and decreasing speed.
Acceleration
Don’t athletes have to make quick changes in acceleration?
Can you think of any equipment used by athletes to help with this?
Connections…
Yes! Examples include:
-starting blocks for runners-cleats on shoes-rubber soled shoes -special clothing
Force: push or pull on an object; changes in the movementEx: hitting a tennis ball, gravity on your body,
pool, etc.
Force = mass x acceleration
What is force?
Net force: when two or more forces act on an object at the same timeBalanced: equal forces acting in opposite
directionUnbalanced: unequal forces acting in opposite
direction
Net Force
Newton’s Laws of Motion