Download - KINEMATIC KONCEPTS. Motion A change in position over time with respect to a reference point
KINEMATIC KONCEPTS
Motion
A change in position over time with respect to a reference point.
Scalar vs. Vector Quantities
Time Temperature Mass
Vector, the villain Force Velocity Acceleration
Scalar: Magnitude onlyVector: Magnitude and Direction
CFU #1: Sort these into Scalar and Vector quantities.
0. 5 meters 30 m/sec, East 5 mi., North 20 degrees
Celsius 256 bytes 4000 Calories
Scalar 0.5 meters 20 degrees
Celsius 256 bytes 4000 Calories
Vector 30 m/sec, East 5 mi., North
Distance vs. Displacement
Distance: total length travelled
Displacement: Change in position
CFU#2 Distance vs. Displacement A car moves 65
km due East, then 45 km due West. A. What distance
was travelled? B. What is the
total displacement?
Answer: A. Distance =
110. km B. Displacement
= 20. km, due East.
65 km
45 km20 km
CFU#3 Distance vs. DisplacementBelow is the graph of the position of a quadcopter over time. The positive direction is above the ground. A. What distance does
the quadcopter travel in the 7 seconds?
Answer: 1.3 meters (0.8 meters up plus 0.5 meters down)B. What is the position of
the quadcopter after 7 seconds?
Answer: 0.5 m above the ground.C. What is the
displacement of the quadcopter in the 7 seconds?
Answer: 0.3 meters, up (It began 0.2 meters above the ground and ended 0.5 meters above the ground.)
Average Speed: a scalar quantity
typical units are m/s or km/h Basic problem solving steps:
ID givens and unknown List and label, including units Check units. Convert if necessary. ID needed equation. Add to list. Isolate unknown in equation. Plug in and solve. Remember units and SF
distance
speed time
Practice Problem
You ride your bike for 30. minutes at an average speed of 15 km/h. How far did you go?
CFU#4-7
Solve the problems on your paper, making sure to follow the problem solving tips.
Answers: 4. 71 km/h 5. 0.60 h 6. 61 m or .061 km 7. a. 2.2 h b. 4.0 h c. 55 km/h
d. 0!!
distance
speed time
Avg. Speed vs. Avg. Velocity
or This is a vector
quantity. This is what we have
been solving when we find slope on a position vs. time graph
Speed: distance per timeVelocity: displacement per time
This is a scalar quantity
Avg. Speed vs. Avg. Velocity
Your textbook does not make a distinction between average speed and average velocity, although there is a difference. It will always say average velocity.
We will explore the subtle differences between average speed and velocity a little later… Δd or Δx
v Δt
CFU #8
A cyclist maintains a constant velocity of +5.0 m/s. Make a table showing the position of the
cyclist every 10.0s for 60.0s (start at 0.0, 0.0)
At time t = 0.0, the cyclist is +250 m from point A. How might you show this on a graph? Δd or Δx
v Δt
vs.
Remember this problem? (CFU #2) A car moves 65 km due East, then 45 km
due West. The distance travelled was 110. km, and the
displacement was 20. km, East. CFU #9 If the trip took 2.5 hours, what is
the average speed? What is the average velocity? Answer: avg. speed = 44 km/hr, v = 8.0 km/hr,
East
vs.
Remember this problem? (CFU #3)
CFU #10 Calculate the average speed and average velocity for the quadcopter.Answers: Average Speed = (1.3 m/7 sec) = 0 .19 m/s = 0.2
m/sAverage Velocity = (0.3m/7 sec) = 0.04 m/s, Up
Hi-Lo: A game of average speed and average velocity
Everyone starts at 0 on the gameboard (2 metersticks) Positive displacements are to the right, negative to the
left. For each turn, roll a 4-sided die and a 6-sided die.
4-sided die represents the magnitude of your displacement in 10 km increments. 6-sided die represents the direction of your displacement: evens are positive, odds are
negative.
Move your game piece the indicated displacement (cms represent kms)and record your move in the table. Then compute the rest of the columns in the table, and plot your position on the position vs. time graph.
Each turn represents one hour of time. At the end of the game, the winner has the greatest
difference between the magnitudes of their average speed and their average velocity.