Acceleration
Change in velocity in a specific time interval. It is measured in m/s2
- Positive acceleration
- When the change of both the magnitude of the velocity
and the direction are positive.
- When the change in both the magnitude of the velocity
and the direction are negative
Negative acceleration
- When the change in the magnitude of the velocity is
negative while the direction is positive.
- When the change in magnitude of the velocity is
positive and the direction is negative.
Formulas:
acceleration = change in velocity
time interval
a=
v
t
where
v = vfinal - vinitial
SO
a = vf - vi
t
*** if they only want the magnitude of acceleration then
ignore the vectors ***
Lets rearrange the formula...
a = vf - vi
t
Solve for t
Solve for vf
A car driver applies the brakes and slows down from 15.0m/s [E]
to 5.00m/s [E] in 4.00s. Determine the car's acceleration.
An object starts from rest and accelerates at 1.30m/s2 [N] for
8.00s. What is the final velocity of the object?
An object initially at rest is dropped off a building and
accelerates to Earth at -9.81 m/s2 [downward]. How long
will it take for the object to reach a final velocity of
-49.1m/s [downward]?
Position vs Time Graphs
Positive
Negative
A curved line means some sort of
accelerated motion.
Increasing slope = positive acceleration
Decreasing slope = negative acceleration
A linear line = no acceleration
Act out the motion:
Velocity vs Time Graphs
Positive acceleration is a linear line with a positive slope.
Negative acceleration is a linear line with negative slope.
No acceleration is a horizontal line.
Act out the motion
Rough sketch the velocity vs time and the
position vs time graphs for the following
situations
Questions:
Pg: 147 #12,13,14,15
Pg 149 # 16
Pg 153 #17
Pg 154 # 1,2,3,4,5,6,7,8,9,11