The Change in Position in a Given Amount of Time
Motion
The change in position in a given amount of time
Georgia Performance Standards
SPS8. Students will determine relationships among force, mass, and motion.
a. Calculate velocity and acceleration.
Frame of Reference
•The Background to which you compare the motion
•This changes your perspective of motion
•______is the most common frame of reference.
•Examples:
Speed
•If the car is moving 60 mi/hr. What does that mean?
•It moves 60 miles every 1 hour.
Speed is the ______covered in a certain amount
of time.
Speed = Distance / Time
Average Speed= Total Distance/Total Time
Instantaneous speed = the speed at a given point
Example: look on your speedometer
Calculating Speed
•If Audrey rides her bike 200 meters in 45 seconds? What is her speed? ______
200 meters
What units do you use?______
Calculating Distance
•If a dog runs at a speed of 15 m/s for 1.5 minutes (90 seconds), what distance does he travel? ______
??
What units do you measure distance in?______
Calculating Time
•If a monkey is catapulted at a speed of 2.5 m/s, how long would it take for it to reach the target 50 meters away?
50 meters
What units would you use??______
Velocity
•Velocity is ______in a given direction.
•Formula for velocity:
Velocity = ______/ Time (+ direction)
•May use the speed formula with direction for velocity.
•Velocity IS A VECTOR. A vector is an arrow that shows magnitude and direction.
Examples of velocity: 45 km/hr East, 200 m/s Northwest
How is it possible for a two cars traveling on the same
road to have the same speed, but different velocities?
Calculating Net Velocity
(Total Velocity)
When two objects are moving in OPPOSITE directions in
relation to each other, you SUBTRACT to get the net velocity.
Net Velocity (of dog in relation to the ground)
=______km/hr right
7 km/hr
70 km/hr
Calculating Net Velocity
(Total Velocity)
When two objects are moving in the SAME direction in
relation to each other, you ADD to get the net velocity.
3 km/hr
Net Velocity (of dog in relation to ground)
= ______km/hr right
70 km/hr
Acceleration
•A change in ______in a given amount of time
•Acceleration Formula: A = Vf – Vi
------
Time
•Final Velocity – Initial Velocity/ Time
Question: Is acceleration affected by direction?
•If a dog is walking down the sidewalk at 2.5 m/sec and sees a cat and speeds up to 7 m/sec in 3 seconds flat, what is his rate of acceleration?
7 m/sec
3 sec
Vf = 7 m/s, Vi = 2.5 m/s,
Time= 3 sec
7-2.5/ 3 = ______
What units are used for acceleration?
______
Deceleration
•Sometimes called “negative acceleration”
•When calculating deceleration, use the formula for acceleration, but the answer will be negative
If a little boy is riding a skateboard at 5 m/sec and hits some gravel and slows down rapidly (in 2 seconds) to a stop. What is his rate of deceleration?
Vf =0, Vi= 5 m/s , Time= 2 sec
0-5/2 = ______m/s
0 m/s
2 sec
5 m/sec
Motion
•Question for you… if you are on a merry go round moving at a constant speed… which of the following would be changing… speed, direction, velocity and/or acceleration. Explain your answer.
