Kinematics Intro

Mechanics A branch of physics that studies motion Kinematics-motion of objects using words, diagrams, numbers, graphs, and equations

Scalars Vs Vectors Described only by magnitude or numerical value only Quantities described by both magnitude and direction

Scalar 5m Vector 9 mi. North 30m/sec, east 20 Degrees c. 265 Bytes Quantity Category (Scalar or vector) Scalar Vector 5m 9 mi. North 30m/sec, east 20 Degrees c. 265 Bytes 4000 Calories

Distance Vs. Displacement scalar quantity  how much ground an object has covered" during its motion. a vector quantity  refers to "how far out of place an object is"; the object's overall change in position.

A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. Even though the physics teacher has walked a total distance of 12 meters, her displacement is 0 meters. During the course of her motion, she has "covered 12 meters of ground" (distance = 12 m). Yet when she is finished walking, she is not "out of place" - i.e., there is no displacement for her motion (displacement = 0 m). Displacement, being a vector quantity, must give attention to direction. The 4 meters east cancels the 4 meters west; and the 2 meters south cancels the 2 meters north. Vector quantities such as displacement are direction aware. Scalar quantities such as distance are ignorant of direction. In determining the overall distance traveled by the physics teachers, the various directions of motion can be ignored.

 Use the diagram to determine the resulting displacement and the distance traveled The skier covers a distance of (180 m + 140 m + 100 m) = 420 mand has a displacement of 140 m, rightward.

1. What is the displacement of the cross-country team if they begin at the school, run 10 miles and finish back at the school? While they have covered a distance of 10 miles, they are not "out of place" or displaced. They finish where they started. Round-trip motions always have a displacement of 0. The displacement of the runners is 0 miles.

2. What is the distance and the displacement of the race car drivers in the Indy 500? near 0 miles The displacement of the cars is somewhere near 0 miles since they virtually finish where they started. Yet the successful cars have covered a distance of 500 miles.

Velocity Velocity is a vector quantity "the rate at which an object changes its position." one step forward and one step back  e.x. When determining velocity you must keep track of direction

Instantaneous speed vs average speed Student login YXJT7CKTF Calculate the speed of this vehicle S=d/t Speed= 5miles/0.2 hours = 25 miles/hour

Q: While on vacation, Lisa Carr traveled a total distance of 440 miles Q: While on vacation, Lisa Carr traveled a total distance of 440 miles. Her trip took 8 hours. What was her average speed?

 A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. The entire motion lasted for 24 seconds. Find V, and S

The physics teacher walked a distance of 12 meters in 24 seconds; thus, her average speed was 0.50 m/s. However, since her displacement is 0 meters, her average velocity is 0 m/s. 

Find Speed and Velocity

The skier has an average speed of (420 m) / (3 min) = 140 m/min and an average velocity of (140 m, right) / (3 min) = 46.7 m/min, right

Acceleration Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. If an object is speeding up or slowing down it has acceleration Sports announcers will occasionally say that a person is accelerating if he/she is moving fast. Yet acceleration has nothing to do with going fast. A person can be moving very fast and still not be accelerating. Acceleration has to do with changing how fast an object is moving. If an object is not changing its velocity, then the object is not accelerating.

Which car is accellerating?

Which car has the greatest accelleration

Match the car to the graph.

Acceleration = changing velocity

Calculating the Average Acceleration Acceleration units= m/s/s, mi/hr/s, km/hr/s, m/s2

The direction of acceleration vector If object is speeding up acceleration is positive If acceleration is slowing down its negetive

http://www.physicsclassroom.com/mmedia/kinema/avd.gif

Pick any two points and calculate acceleration using the equation

Answer: a = 2 m/s/s Use a = (vf - vi) / t and pick any two points Answer: a = 2 m/s/s Use a = (vf - vi) / t and pick any two points. a = (8 m/s - 0 m/s) / (4 s)a = (8 m/s) / (4 s) a = 2 m/s/s

Use equation to calculate acceleratoin

Answer: a = -2 m/s/s Use a = (vf-vi) / t and pick any two points Answer: a = -2 m/s/s Use a = (vf-vi) / t and pick any two points. a = (0 m/s - 8 m/s) / (4 s)a = (-8 m/s) / (4 s) a = -2 m/s/s

ideas Acceleration video World faster sports car acceleration problem