before warm up problem go onto turnitin.com and make sure you can log into the correct period...
TRANSCRIPT
Before Warm up ProblemGo onto Turnitin.com and make sure you can log into the correct period
Code/PasswordPeriod1 – 8549371 / JecaPhys1Period 3 – 8549395 / JecaPhys3Period 4 – 8549411 / JecaPhys4Period 6 – 8549441 / JecaPhys6Period 7 – 8554589 / JecaPhys7Period 8 – 8554628 / JecaPhys8
Warm up ProblemA bus travels 280 km south along a straight path with an average velocity of 24.4 m/s to the south. The bus stops for 24 min, then it travels 210 km south with an average velocity of 20.8 m/s to the south.
a. How long does the total trip last?
b. What is the average velocity for the total trip?
Physics Honors A & B – Day 9/10/13 & 9/11/13Motion in 1D cont.
AgendaAcceleration?velocity v. time plotsKinematic equationsexamples
What is acceleration?
AccelerationAcceleration measures the rate of change in velocity per time
Units
Acceleration is a vectorPositive or negative means left or right direction
AccelerationDirection of acceleration will affect the magnitude and
direction of velocity. Depending on Velocity vector, it could cause speeding up or
slowing down.
�⃗�
�⃗�
AccelerationDirection of acceleration will affect the magnitude and
direction of velocity. Depending on Velocity vector, it could cause speeding up or
slowing down.
�⃗�
�⃗�
AccelerationDirection of acceleration will affect the magnitude and
direction of velocity. Depending on Velocity vector, it could cause speeding up or
slowing down.
�⃗�
�⃗�
AccelerationDirection of acceleration will affect the magnitude and
direction of velocity. Depending on Velocity vector, it could cause speeding up or
slowing down.
�⃗�
�⃗�
Acceleration+v and +a speed up
+v and –a slow down
-v and –a speed up
-v and +aslow down
v = 0 and + a speed up in direction of a
v = 0 and –a speed up in direction of a
+ v and a = 0 constant velocity (No change)
-v and a = 0 constant velocity (No change)
AccelerationRecall rate of change in velocity
Slope
If velocitywent on the y-axis 𝑣
𝑡
And t went on the x-axis
Velocity v. time plot
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.2
0.4
0.6
0.8
1
1.2
Time (s)
Ve
loc
ity
(m
/s)
Velocity v. time plot
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.2
0.4
0.6
0.8
1
1.2
Time (s)
Ve
loc
ity
(m/s
)
Use
𝑡1
v 1
v 2
Velocity v. time plot
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.2
0.4
0.6
0.8
1
1.2
Time (s)
Ve
loc
ity
(m
/s)
𝑡1
v 1
𝑡 2
v 2
So let’s look back How would you get from a Position v. time plot to acceleration v. time
Calculate acceleration from Position v. time plot
0 0.5 1 1.5 2 2.5 30
0.2
0.4
0.6
0.8
1
1.2
Time (s)
Po
sit
ion
(m
)
What would be ?
Calculate acceleration from Position v. time plot
0 0.5 1 1.5 2 2.5 30
0.2
0.4
0.6
0.8
1
1.2
Time (s)
Po
sit
ion
(m
)
What would be ?
Calculate acceleration from Position v. time plot
0 0.5 1 1.5 2 2.5 30
5
10
15
20
25
30
35
Time (s)
Po
sit
ion
(m
)
What would be ?
But we have word problems How are we going to solve the word problems we normally get?
Kinematic Equations for constant acceleration
All equations valid for constant acceleration
ExampleA car accelerates uniformly from rest to a velocity of +23.7 m/s in 6.5 s. a) What was it’s acceleration? b) What was the car’s displacement?
Draw a picture.Write down the given values. Write down what we are looking for.Write down the equation we need to use. Convert units.Manipulate equation. Input number with units. Calculate answer with correct units.Clearly mark answer.
ExampleA car with an initial speed of +4.0 accelerates uniformly at a rate of +3.0 . Find the final velocity and the displacement after 5.0 s.
Draw a picture.Write down the given values. Write down what we are looking for.Write down the equation we need to use. Convert units.Manipulate equation. Input number with units. Calculate answer with correct units.Clearly mark answer.