-Measure a change in velocity (acceleration) of a cart on a ramp using a motion detector.
-Construct graphs of the motion of a cart on a ramp.
-Define acceleration using words and an equation.
-Calculate speed, distance, and time using the equation for acceleration.
-Interpret distance-time and velocity-time graphs for different types of motion.
What do you see/ What do you think?
Wednesday, October 5th
I see a red cat that is speeding up within a matter of a small amount of time. The Man and the dog look like they were crossing the street, and then they ran because the red car started to speed up. What are some differences and similarities of the motion of these 2 vehicles as each goes from a stop to f 30 mi/h?
The car reaches the top speed faster than the bus. the car has greater friction with the road.
Investigation
Wednesday, October 5th
-Tangent line: line that only touches a curve at one point. -Slope of the tangent: the instantaneous velocity at a specific point in time.
1. If you were to place the cart at the top of the ramp and release it to freely move down the ramp would it move through the first half of the distance in the same amount of time as the second half of the distance? Why or why not?
No it would not because the car builds up momentum and speed as it moves down the hill.
2. Below are four different distance vs time graphs. Copy and paste the graphs with their correct descriptions of motion into your wiki.
Screen_shot_2011-10-05_at_9.13.09_AM.png
Screen_shot_2011-10-05_at_9.13.09_AM.png
Screen_shot_2011-10-05_at_9.13.18_AM.png
Screen_shot_2011-10-05_at_9.13.18_AM.png
--------------> Moves slowly and then accelerates.
Screen_shot_2011-10-05_at_9.13.13_AM.png
Screen_shot_2011-10-05_at_9.13.13_AM.png
Screen_shot_2011-10-05_at_9.13.24_AM.png
Screen_shot_2011-10-05_at_9.13.24_AM.png
-------------->Moves fast and then slows down.
How is the velocity changing with respect to time? As time increases, velocity increases.
Tangent Line- The tangent line is at the same position and time in the distance and velocity graphs. Slope=
Tangent Line 1
1a.png
1a.png
Tangent Line 2
2a.png
2a.png
Velocity
1b_&_2a.png
1b_&_2a.png
Velocity Time Graph-
1b_&_2a.png
1b_&_2a.png
(1 meter per second)
.664 is the
Calculate Acceleration:
Physics Talk:
Wednesday, October 5th
Physics Words: Vector: a quantity that has both magnitude and direction Negative acceleration: a decrease in velocity with respect to time. The object can slow down or speed up. Positive Acceleration: an increase in velocity with respect to time. The object can speed up or slow down.
1. Acceleration = change in velocity/change in time
a= ∆v
∆t
2. Meters per seconds squared; (m/s)/s 3. A vector quantity is a quantity that has both magnitude and direction. Scalar quantity is described by magnitude alone. 4. Constant velocity graph:
Screen_shot_2011-10-05_at_3.25.22_PM.png
Screen_shot_2011-10-05_at_3.25.22_PM.png
Constant acceleration graph:
Screen_shot_2011-10-05_at_3.25.40_PM.png
Screen_shot_2011-10-05_at_3.25.40_PM.png
5. The slope of a graph represents the rate of acceleration or deceleration.
Physics Words: Acceleration: the change in velocity with respect to a change in time Vector: a quantity has both magnitude and direction Negative acceleration: a decrease in velocity with respect to time. The object can slow down (20 m/s to 10 m/s or speed up (-20 m/s to -30 m/s) Positive acceleration: an increase in velocity with respect to time. The object can speed up (20 m/s to 30 m/s) or slow down (-20 m/s to -10 m/s) Tangent line: a straight line that touches a curve in only one point
Checking Up Questions: 1. Give the defining equation for acceleration in words, and by using symbols.
Acceleration is the change in velocity with respect to time. a=∆v/∆t 2. What is an SI unit for measuring acceleration? Use words and unit symbols to decribe the unit.
The SI unit is (m/s)/s or m/s^2, (km/h)/s, or ft/s^2. 3. What is the difference between a vector and a scalar quantity?
A quantity that involves both direction and size (magnitude is called a vector quantity (ex. velocity...indicates a change in position over a period of time and the direction). A quantity that has size, but not direction, is called a scalar quantity (ex. speed...only indicates the change in position over a period of time in a straight line). 4. Sketch a distance-time graph for
a) constant velocity:
Activity: Car vs Truck vs Bus
Friday, October 7th
Photo_on_2011-10-10_at_16.59.jpg
DoNow: Physics Talk Review
Friday, October 7th
1. a= 30/5= 6m/s^2
2. Vectors: Velocity, Force (push and pull)
Scalar: Speed, Calories, Anything you can count. A vector involves direction and speed. A scalar involves size but no direction.
Physics To Go #1-16 pg. 68
Due Thursday, October 13th 1.) Can a situation exist in which an object has zero acceleration and nonzero velocity? Explain. No, an object can never have 0 acceleration with a nonzero velocity whenever you are moving, that is your velottiy. You divide that by the time it took you to travel that speed and you would get acceleration. You would never get 0 unless you had 0m/s for your velocity. 2.)Can a situation exist in which an object has zero velocity and nonzero acceleration, even for an instant? Explain.
No, an object can never have 0 velocity because for it have 0 velocity it would need to also have 0 acceleration because anything divided by 0 is zero. 3.)If two automobiles have the same acceleration, do they have the same velocity? Why or why not?
They don't need to have the same velocity because they could have the same acceleration but could not have achieved it in the same velocity. For example, they could both have 5 m/s for acceleration but one velocity can be 25m and the other one could be 15m. 4.)If two automobiles have the same velocity, do they have the same acceleration? Why or why not?
They don't need to have the same acceleration to have the same velocity because they could have achieved that velocity in a different amount of time. 20m could have been achieved in 5s or 2s leaving it with different accelerations. 5.)Can an accelerating automobile be overtaken by an automobile moving with constant velocity?
No because eventually the accelerating automobile will catch up. 6.) Is it correct to refer to speed-limit signs instead of velocity-limit signs? Why or why not? What units are assumed for speed limit signs in the U.S.?
We refer to speed-limit signs because velocity only refers to speed in a certain direction where speed limit signs are in speeds in every direction. It is better for drivers to see. The units associated with speed-limit signs are miles per hour. 7.) Suppose an automobile were accelerating at 2mi/hr every 5s and could keep accelerating for 2 min at that rate.
a). a=∆v/∆t
a=2mi/h
v= ?
t= 120s/5s= 24s
2=∆v/24 ∆v= 48mi/s
b). d= vt
d= (48 8.) At an international auto race, a race car leaves the pit after a refueling stop and accelerates uniformly to a speed of 75 m/s in 9s to rejoin the race. A. What is the racecars acceleration at this time?
a=∆v/∆t
a=75/9
a=8.3 mi/s
B. What was the race cars average speed during the acceleration?
C. How far does the race car go during the time it is accelerating?
D. A second race car leaves after its pit stop and accelerates to 75 mi/s in 8s. Compared to the first face car, what is this race cars acceleration, average speed during the acceleration, and distance traveled?
14.) a). Vf= ?
a= 9.8 m/s^2
Vi= 0 m/s
∆t= 4.516 s
9.8= Vf-0 / 4.516 Vf= 44.26 m/s
b). 100m=1/2(9.8m/s^2)∆t^2 t= 4.51 seconds
c). a=∆v/∆t
9.8m/s^2= ∆v/ 10s ∆v= 98 m/s
d). d=1/2(9.8)(10)^2 d= 490m
e). The answers would have to be around 6 times less on the Moon than on Earth.
Learning OutcomesWednesday, October 5th
-Measure a change in velocity (acceleration) of a cart on a ramp using a motion detector.
-Construct graphs of the motion of a cart on a ramp.
-Define acceleration using words and an equation.
-Calculate speed, distance, and time using the equation for acceleration.
-Interpret distance-time and velocity-time graphs for different types of motion.
What do you see/ What do you think?
Wednesday, October 5th
I see a red cat that is speeding up within a matter of a small amount of time. The Man and the dog look like they were crossing the street, and then they ran because the red car started to speed up.
What are some differences and similarities of the motion of these 2 vehicles as each goes from a stop to f 30 mi/h?
The car reaches the top speed faster than the bus. the car has greater friction with the road.
Investigation
Wednesday, October 5th
-Tangent line: line that only touches a curve at one point.
-Slope of the tangent: the instantaneous velocity at a specific point in time.
1. If you were to place the cart at the top of the ramp and release it to freely move down the ramp would it move through the first half of the distance in the same amount of time as the second half of the distance? Why or why not?
No it would not because the car builds up momentum and speed as it moves down the hill.
2. Below are four different distance vs time graphs. Copy and paste the graphs with their correct descriptions of motion into your wiki.
How is the velocity changing with respect to time?
As time increases, velocity increases.
Tangent Line- The tangent line is at the same position and time in the distance and velocity graphs.
Slope=
Tangent Line 1
Tangent Line 2
Velocity
Velocity Time Graph-
(1 meter per second)
.664 is the
Calculate Acceleration:
Physics Talk:
Wednesday, October 5th
Physics Words:
Vector: a quantity that has both magnitude and direction
Negative acceleration: a decrease in velocity with respect to time. The object can slow down or speed up.
Positive Acceleration: an increase in velocity with respect to time. The object can speed up or slow down.
1. Acceleration = change in velocity/change in time
a= ∆v
∆t
2. Meters per seconds squared; (m/s)/s
3. A vector quantity is a quantity that has both magnitude and direction. Scalar quantity is described by magnitude alone.
4. Constant velocity graph:
Constant acceleration graph:
5. The slope of a graph represents the rate of acceleration or deceleration.
(1 meter per second)
.664
Calculate Acceleration-
rise/run
∆v/∆t
.6/1.1= .55 meters/second squared
3. Predict-
Tangent Line- Velocity increases as time goes on.
Homework:
Thursday, September 6th
Physics Words:
Acceleration: the change in velocity with respect to a change in time
Vector: a quantity has both magnitude and direction
Negative acceleration: a decrease in velocity with respect to time. The object can slow down (20 m/s to 10 m/s or speed up (-20 m/s to -30 m/s)
Positive acceleration: an increase in velocity with respect to time. The object can speed up (20 m/s to 30 m/s) or slow down (-20 m/s to -10 m/s)
Tangent line: a straight line that touches a curve in only one point
Checking Up Questions:
1. Give the defining equation for acceleration in words, and by using symbols.
Acceleration is the change in velocity with respect to time. a=∆v/∆t
2. What is an SI unit for measuring acceleration? Use words and unit symbols to decribe the unit.
The SI unit is (m/s)/s or m/s^2, (km/h)/s, or ft/s^2.
3. What is the difference between a vector and a scalar quantity?
A quantity that involves both direction and size (magnitude is called a vector quantity (ex. velocity...indicates a change in position over a period of time and the direction). A quantity that has size, but not direction, is called a scalar quantity (ex. speed...only indicates the change in position over a period of time in a straight line).
4. Sketch a distance-time graph for
a) constant velocity:
Activity: Car vs Truck vs Bus
Friday, October 7th
DoNow: Physics Talk Review
Friday, October 7th
1. a= 30/5= 6m/s^2
2. Vectors: Velocity, Force (push and pull)
Scalar: Speed, Calories, Anything you can count. A vector involves direction and speed. A scalar involves size but no direction.
Physics To Go #1-16 pg. 68
Due Thursday, October 13th
1.) Can a situation exist in which an object has zero acceleration and nonzero velocity? Explain.
No, an object can never have 0 acceleration with a nonzero velocity whenever you are moving, that is your velottiy. You divide that by the time it took you to travel that speed and you would get acceleration. You would never get 0 unless you had 0m/s for your velocity.
2.)Can a situation exist in which an object has zero velocity and nonzero acceleration, even for an instant? Explain.
No, an object can never have 0 velocity because for it have 0 velocity it would need to also have 0 acceleration because anything divided by 0 is zero.
3.)If two automobiles have the same acceleration, do they have the same velocity? Why or why not?
They don't need to have the same velocity because they could have the same acceleration but could not have achieved it in the same velocity. For example, they could both have 5 m/s for acceleration but one velocity can be 25m and the other one could be 15m.
4.)If two automobiles have the same velocity, do they have the same acceleration? Why or why not?
They don't need to have the same acceleration to have the same velocity because they could have achieved that velocity in a different amount of time. 20m could have been achieved in 5s or 2s leaving it with different accelerations.
5.)Can an accelerating automobile be overtaken by an automobile moving with constant velocity?
No because eventually the accelerating automobile will catch up.
6.) Is it correct to refer to speed-limit signs instead of velocity-limit signs? Why or why not? What units are assumed for speed limit signs in the U.S.?
We refer to speed-limit signs because velocity only refers to speed in a certain direction where speed limit signs are in speeds in every direction. It is better for drivers to see. The units associated with speed-limit signs are miles per hour.
7.) Suppose an automobile were accelerating at 2mi/hr every 5s and could keep accelerating for 2 min at that rate.
a). a=∆v/∆t
a=2mi/h
v= ?
t= 120s/5s= 24s
2=∆v/24
∆v= 48mi/s
b). d= vt
d= (48
8.) At an international auto race, a race car leaves the pit after a refueling stop and accelerates uniformly to a speed of 75 m/s in 9s to rejoin the race.
A. What is the racecars acceleration at this time?
a=∆v/∆t
a=75/9
a=8.3 mi/s
B. What was the race cars average speed during the acceleration?
C. How far does the race car go during the time it is accelerating?
D. A second race car leaves after its pit stop and accelerates to 75 mi/s in 8s. Compared to the first face car, what is this race cars acceleration, average speed during the acceleration, and distance traveled?
9.) a). a=∆v/∆t
a= (.6-4.5)/(1.3-0)
a= -3 m/s
b). d=1/2at^2
d=1/2(-3)(1.3)^2
c). d=1/2(3)(1.1)62
d= 1.8
d= Trial 2
10.) a). Around 12m/s
b). a=∆v/∆t
a= (9)/(7.5)
a= 1.2m/s
c). It would have picked up speed and the final velocity would have been greater.
11.) a). B
b). D
c). E
d). A
e). F
f). C
12.) a). ef,
b). ac
c). ce
d). eg
e). 700m
f). 0m. Back at the starting point
13.) a). a=∆v/∆t
a= (250)/(30)
a= 8.3m/h/s (After each seconds he is gaining 8.3 mi/h.)
b). ∆t= 45 sec
Vf= ?
Vi= 0mi/hr
a= 8.33 mi/hr/sec
8.33=Vf-0 / 45
Vf= 374.85= 375mi/h
c). Vf= 500 mi/h
Vi= 250 mi/h
∆t= ?
a= 8.33 mi/hr/sec
8.33= (500)-(250) / ∆t
8.33= 250/ ∆t
∆t= 30.01 seconds x2 (because of going from 0 to 500 mi/h)
60 seconds
d). d= 1/2at^2
d=1/2(8.33)(60)^2
d=15000 m
14.) a). Vf= ?
a= 9.8 m/s^2
Vi= 0 m/s
∆t= 4.516 s
9.8= Vf-0 / 4.516
Vf= 44.26 m/s
b). 100m=1/2(9.8m/s^2)∆t^2
t= 4.51 seconds
c). a=∆v/∆t
9.8m/s^2= ∆v/ 10s
∆v= 98 m/s
d). d=1/2(9.8)(10)^2
d= 490m
e). The answers would have to be around 6 times less on the Moon than on Earth.
(16)
a). 1.0 seconds
d= 1/2(4)(1)^2
d= 2 meters
b). 2.0 seconds
d=1/2(4)(2)^2
d= 8 meters
c). 3.0 seconds
d=1/2(4)(3)^2
d= 18 meters
d). 4.0 seconds
d=1/2(4)(4)^2
d= 32 meters
Speeding Up / Slowing Down
Wednesday, October 12th
Speeding Up
Slowing Down
Questions/Answers for speeding up and slowing down:
Active Physics Plus:
Wednesday, October 12th
d= 1/2at^2 + Vit
1. Vf = 20 m/s
Vi= 7 m/s
a= 3 m/s^2
∆t= ?
a= Vf-Vi
∆t
3 m/s^2= 20 m/s - 7 m/s ––> ∆t (3m/s^2) = (20 m/s - 7 m/s) ––> ∆t = 4.33 sec
1 3 3 m/s^2 3m/s^2
2. a= 1.5 m/s^2
∆t= 10 seconds
Vi= 7 m/s
Vf= ?
1.5 = Vf - 7 m/s ––> 1.5(10) = Vf - 7 m/s ––> Vf = 22 m/s
10s
3a. a= ∆v/∆t
Vf=20 m/s
Vi= 0 m/s
∆t= 5 sec
a=?
a= 20 m/s - 0 m/s ––> a= 4 m/s^2
5 sec
3b. d= 1/2at^2
d= ?
a= 4 m/s^2
t= 5 sec
d= 1/12 (4 m/s^2)(5 sec) ––> d= 50 m
4. a= 4 m/s^2
∆t= 10 sec
d=?
d= 1/2at^2
d= (1/2)(4 m/s^2)(10 sec) ––> d= 200 m