Kinematics (Velocity) Learning Outcome C1

Transcription

1 Kinematics (Velocity) Learning Outcome C1 C1 apply knowledge of the relationship between time, displacement, distance, velocity, and speed to situations involving objects in one dimension. Student Achievement Indicators Students should be able to demonstrate the following: Differentiate between scalar and vector quantities. Define distance, displacement, speed and velocity. Construct displacement-time graphs, based on data. Use a displacement-time graph to determine: Displacement and distance Average velocity and speed Instantaneous velocity and speed Solve problems involving: Displacement Time Average velocity Construct velocity-time graphs, collecting data from a variety of sources. Use velocity-time graphs to determine velocity, displacement and average velocity. For Learning Scalar vs. Vector Review Assignment (Gr. 10 Review) Distance, Position and Displacement Assignment (Gr. 10 Review) Practice Assignment (Merrill) pg. 33 #18-22 Practice Assignment (Merrill) pg. 34 #23 & 24 Practice Assignment (Merrill) pg. 112 #1,3 & 4a Practice Assignment (Gore) pg. 11 #1-7 Practice Assignment (Merrill) pg. 45 #1 & 2 Practice Assignment (Merrill) pg. 47 #5-7 Practice Assignment (Merrill) pg. 53 #9-11 Practice Assignment (Gore) pg. 19 #1-9 Of Learning Learning Outcome C1 Assignment #1 (Introduction to Kinematics) Learning Outcome C1 Quiz #1 (Introduction to Kinematics) Lab 1-2: The Frequency of a Recording Timer (Gore) pg. 9 Lab 1-3: Measuring the Speed of a Model Car (Gore) pg. 10 & 11 Learning Outcome C1 Assignment #2 (Position-Time Graphs) Learning Outcome C1 Quiz #2 (Position-Time Graphs) Learning Outcome C1 Test

2 Grade 10 Physics Review Scalar quantities have magnitude but no direction. Example distance, speed, time, energy and density Vector quantities have both magnitude (size) and direction Example velocity, force, momentum and displacement Distance is the total amount traveled, while displacement takes into account direction. This means that displacement is in relation to the starting point or a specific reference point. Velocity Equations from Gr. 10 v = v f - v i d = d f - d i t = t f - t i Where: d = distance or displacement (if direction) v = speed or velocity (if direction t = time Solving Algebraic Equations Example 1 - ; solve for t Remember in order to isolate t you must do the opposite operation, so in this case the opposite of multiplication is division =

3 Example 1 Julie walked 2m (east), 6m (east) and then walked 8m (west) a. Calculate the distance Julie walked. Distance is a scalar quantity, therefore ignore direction. Total distance = 2m + 6m + 8m = 16m b. Calculate Julie s total displacement. Displacement is a vector quantity, so direction must be considered, since east and west are opposite let west be a negative integer. d = 2m + 6m -8m = 0m (East or West) Example 2 - a dog moves around the backyard (see Figure 5.1 pg. 95 Gore) a. Calculate the distance d = 3.0m + 2.0m + 4.0m + 4.0m + 2.0m + 4.0m = 19.0m b. Calculate displacement ***Use a protractor and ruler*** This problem is shown using a vector diagram, in a vector diagram vectors are added tail (arrow head) to head. Example: A vector diagram for this situation would look like this:

4 To calculate displacement this problem must be broken down into horizontal (East/West components) and vertical (North/South) components. Let the North and East be positive and South and West be negative. d (north/south) = 3.0m + 2.0m -2.0m = 3.0m or 3.0m (N) d (east/west) = 4.0m + 4.0m 4.0m = 4.0m or 4.0m (E) Now the displacement must be found from the front porch to the Stop!. This can be done using Pythagorus and trigonometry. Kinematics Is the study of the motion of objects without reference to the cause of the motion. Kinematics is used to describe the motion of an object. Time Any measurement of time involves some sort of event repeating itself at regular intervals. All devices used to measure time contain some sort of regularly vibrating object. Examples pendulum, a quartz crystal or vibrating electrons Cycle Is when an object undergoes regular movement; one complete movement Example pendulum 1 cycle Period Time required for each cycle. Frequency The number of cycles completed in one unit of time. Often measured in rpm s (rep per minute0 Example car engine The frequency of one cycle per minute is called a Hertz (Hz) KHz is a higher frequency

5 Example radio signal frequency 1KHz = 1000 Hz 1MHz = Hz Calculations for Time & Frequency Speed Is the distance traveled per unit of time with no reference to direction Velocity Uses the same formula as speed, but the final answer must include direction in reference to the starting point The symbol for velocity is v with an arrow on top, a small arrow represents a vector quantity. Example 1 a girl walked 20m(E) and then 40m(W) in 5 seconds. Calculate her velocity. -4 m/s or 4m/s(W) Instantaneous Speed Speed at an instant in time. Speedometers in cars calculate instantaneous speed Position-Time Graph Shows how position is related to time If a straight line represents the data; there is a linear relationship between time and position. Displacement is the vertical separation between two points. Time is the horizontal separation between two point. The slope of a line on a position-time graph can be used to calculate velocity.

6 Position (m) Example of a Position-Time Graph 1800 Position-Time Graph Time (s) (forward) The slope of this line is equal to velocity, so a direction must be associated with it. Also remember form Math:

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