period 1 pg. 29-31 ques: 27, 33, 36, 56, 58a, 60-62, 66, 68b
TRANSCRIPT
Period 1
• Pg. 29-31 • Ques: 27, 33, 36, 56, 58a, 60-62, 66, 68b
Warm-Up Questions
• Just think, what is the difference between… – Speed & Velocity?
– Distance & Displacement
1-Dimensional Motion
Motion…(in a straight line)• An object is in motion if…
…it changes position …or… travels a distance
• How do we typically describe motion?– Speed• Units…??– Distance & Time
-- Equation??
Speed vs. Velocity
• What’s the difference?– Speed =
– Velocity =
• Difference btwn. Distance & displacement then?– Dist = total path length an object covered during its
motion– Disp = directional distance between an object’s
starting and ending points of motion
-- Velocity Equation???
Scalar vs. Vector Quantities
• Scalar– Quantities that are described by magnitude alone
• Vector– Quantities that are described by BOTH a
magnitude and direction
Examples: Scalar or Vector??
• Distance = _______• Displacement = _______• Time = _______• Mass = _______• Velocity = _______• Speed = _______• Acceleration = _______
Vector Addition• A vector is represented by an arrow– Drawn to scale and points in the direction of the
motion– NET outcome = resultant vector
***Sum all the vectors in x direction & sum all vectors in y direction, then find magnitude of resultant vector
• Example:– A car drives 5 km east, stops, and drives another 3
km east. Draw the 2 initial vectors and the resultant vector.
Vector Addition• A vector is represented by an arrow– Drawn to scale and points in the direction of the
motion– NET outcome = resultant vector
• Example:– A car drives 2 km east, stops, drives 10 km west,
stops, and then drives another 3 km east again. Draw the 3 initial vectors and the resultant vector.
***Need to Know Equations***
• Avg. Speed =
• Avg. Velocity =
• Final Position =
Question…
• A hiker walks 6 km west and then turns abruptly and immediately walks another 8 km north and stops to catch his breath.– What was the distance that he hiked so far?
– What was the displacement of his hike so far?
Use Trig to find Direction
• A hiker walks 6 km west and then turns abruptly and immediately walks another 8 km north and stops to catch his breath.– What was the displacement of his hike so far?
Question
• A BPHS track star runs the 100 m turn (half circle portion at the end of the track) in 16 s.
• What distance did they run? Displacement?• What was their speed? Velocity?
**Circumference = 2 r **
Warm-Up Question• A jogger jogs 300 m straight in one direction in 2.5
min and then jogs back to the starting point in 3.3 min. What was the jogger’s avg velocity:1. On the way down?
2. On the way back to the starting point?
3. For the total jog?
Distance vs. Displacement Wkst
Instantaneous Velocity
• Defined as:– How fast something is moving in which direction
at a particular instant of time
• When dealing with uniform motion, how are inst. velocity and avg. velocity related?
Graphical Representation
Nonuniform Motion
• How would you find the inst. velocity of an object’s motion that looked like:
Posi
tion
Time
Nonuniform Motion
• How would you find the inst. velocity of an object’s motion that looked like:
Nonuniform Motion
• How would you find the inst. velocity of an object’s motion that looked like:
Math Problems
• Book:– Pg. 60-61 -> 1, 7, 8, 10, 13-14, 16, 21, (22 = Bonus)
Acceleration
• Defined as:–Rate at which velocity changes• Velocity changes when:– An object speeds up or slows down– An object changes its direction of motion
• So when does an object accelerate?
***Need to Know Equations***
• Avg. Acceleration =
• Final Velocity (w/ constant acceleration) =
Acceleration Math
• A car has an initial velocity of 80 m/s. It slows down to a stop in 8 seconds. What was the cars acceleration during this time?
Average Velocity Question…
• What was the average velocity of that car as it constantly accelerated during that time period?
***Need to Know Equations***
• Avg. Acceleration =
• Final Velocity (w/ constant acceleration) =
• Avg. Velocity (w/ constant acceleration) =
Math Problems
• Pg. 61-62 23-27, 30, 32-34
Kinematic Equations
• Some physics problems are hard to do because they require the application of multiple equations throughout one question.
• How can we make our lives easier…?– Let’s combine a couple of our equations
algebraically in advance
Deriving Equations
• Final position w/o avg. velocity & acceleration:– Xf eq:
– Avg. V eq:
– Combined (sub in for avg. v):
Deriving Equations
• Final position w/o avg. velocity & acceleration:
xf = xi + ½(vf + vi)t
Deriving Equations
• Displacement when object accelerates w/o vf:
Deriving Equations
• Displacement when object accelerates w/o vf:– Use previous equation:
– Vf eq:
– Combined (sub in for Vf):
Deriving Equations
• Displacement when object accelerates w/o vf:
xf = xi + vit + ½at2
Deriving Equations
• Displacement when object accelerates from rest:
xf = xi + vit + ½at2
xf = xi + ½at2
xf = ½at2
Deriving Equations
• Displacement, Velocity, & Acceleration w/o Time:– Use Vf eq:
– xf = xi + ½(vf + vi)t eq:
Deriving Equations
• Displacement, Velocity, & Acceleration w/o Time:
Deriving Equations
• Displacement, Velocity, & Acceleration w/o Time:
vf2 = vi
2 + 2a(xf – xi)
Example Math Problem
A rocket is shot horizontally from a soldier’s rocket launcher with a constant acceleration of 20m/s2. After 10 seconds, how fast is the rocket moving & how far has it traveled?
Example Math Problem
A rocket is shot horizontally from a soldier’s rocket launcher with a constant acceleration of 20m/s2. After 10 seconds, how fast is the rocket moving & how far has it traveled?
Math Problems
• Pg. 62 38 - 42
Additional Lab Questions
• What should the slope of the line for the graph that you drew be equal to? (Name & Value…think about rise over run)
• Knowing this, what equation can we then derive to solve for the acceleration of an object on an inclined plane?
• What was the percent error between the extrapolated value and the accepted value of g?
Free Fall
• Defined as:– When an object in motion is influenced only by
the pull of gravity
• Value of Gravity =- 9.8 m/s2
Gravity• Does the acceleration of an object due to
gravity ever change? – Acceleration due to g is constant!• Constant acceleration = which equations???
• Can it be different in different regions on Earth?– YES! Due to….• Distance from Earth’s center• Air resistance
Free Fall Equations
Math Problems
• Pg. 63-64 59-62, 64-67, 70a
The Moving Man
Analyzing Graphs
• Using slope and area of ΔV vs. t graphs to determine ΔX vs. t and a vs. t graphs
Analyzing Graphs
• Using slope and area of ΔV vs. t graphs to determine ΔX vs. t and a vs. t graphs
Analyzing Graphs• Using slope and area of ΔV vs. t graphs to
determine ΔX vs. t and a vs. t graphsVelocity (m/s)
20
15
10
5
Analyzing Graphs
• Using slope and area of ΔV vs. t graphs to determine ΔX vs. t and a vs. t graphs
Velocity (m/s)
20
15
10
5
Analyzing Graphs
• Using slope and area of ΔX vs. t graphs to determine ΔV vs. t and a vs. t graphs
Analyzing Graphs
• Using slope and area of ΔV vs. t graphs to determine ΔX vs. t and a vs. t graphs
Analyzing Graphs
• Using slope and area of ΔV vs. t graphs to determine ΔX vs. t and a vs. t graphs
Analyzing Graphs
• Using slope and area of ΔV vs. t graphs to determine ΔX vs. t and a vs. t graphs