velocity & acceleration velocity *describes both the speed & direction of an object
TRANSCRIPT
VELOCITY & ACCELERATION
VELOCITY*Describes both the speed & direction of an object
VELOCITY Direction*can be expressed using (+) or (-) signs
*up, right or forward are considered to be (+)
*down, left, or backward are considered to be (-)
When can the speed of an object remain constant
while the velocity of the object is changing?
When the object is changing directions!!!!
*the velocity changes
because the direction
changes.
When is the direction of an object always
changing?
*When the object is
turning in a circle.
ACCELERATION
*Rate of change of VELOCITY
ACCELERATION*Occurs when the speed and/or direction of motion changes (Dv)
* during a time interval (Dt)
FORMULA FOR ACCELERATION
*a = Dv / Dt*a = vf - vi / tf - ti
1.) An airplane traveling at a speed of 20 km/min changes to 80 km/min over a distance of 57 km. When the airplane started to speed up it was 1:37 p.m. When the airplane finished its acceleration it was 1:46 p.m. What was the airplane’s acceleration?
Sample problem 1
Need InformationInitial Velocity = 20 km/min Initial Time = 1:37 p.m.Final Velocity = 80 km/min Final Time = 1:46 p.m.
•a = vf - vi / tf - ti
80 km/min - 20 km/min
1:46 - 1:37
a =
60 km/min
9 min
a =
a = 6.67 km/min2
* speeding up is considered to be +
* slowing down is considered to be –
Positive and Negative signs indicate both:
For ACCELERATION…
1.) Direction of Displacement
(Forward/Backward, Left/Right, Up/Down)
2.) Change in Speed(Speeding up, Slowing down)
What is the SIGN of acceleration for a car
speeding up while moving forward?
Speeding up: Positive change in speed
Moving forward: Positive direction of displacement
Positive x Positive =
POSITIVE ACCELERATION
Sample Problem 2
What is the SIGN of acceleration for a car that
is speeding up while moving backwards?
Speeding up: Positive change in speed
Moving backwards: Negative direction of displacement
Positive x Negative =
NEGATIVE ACCELERATION
Sample Problem 3
What is the SIGN of acceleration for a car slowing down while moving backwards?
Slowing down: Negative change in speed
Moving backwards: Negative direction of displacement
Negative x Negative =
POSITIVE ACCELERATION
Sample Problem 4
Negative Acceleration is
NOT the same as Deceleration !!!!
DECELERATION Refers ONLY to the slowing
down of an object
The last sample problem
demonstrated a positive acceleration
sign that included deceleration
Acceleration of Coach McKnight on the Interstate
SPEED
(M/S)
T I M E (SEC.)
“To calculate total distance covered you must color in the graph.”
Acceleration of Coach McKnight on the Interstate
T I M E (SEC.)
SPEED
(M/S)
“To calculate total distance covered you must color in the graph.”