Do NowDo Now

Time (sec.)Time (sec.) Position Position (meters)(meters)

00 00

1.51.5 33

33 77

4.54.5 10.210.2

66 14.514.5

7.57.5 1717

Position vs. Timey = 2.3103x

0

5

10

15

20

0 1 2 3 4 5 6 7 8

Time (sec.)

Posi

tion

(m)

Aim: How can we calculate average Aim: How can we calculate average velocity?velocity?

1)1) Convert 3.4x10Convert 3.4x10-5 -5 Gigavolt to volts.Gigavolt to volts.

2)2) Convert 9.0 grams to milligrams.Convert 9.0 grams to milligrams.

3)3) Convert 6.2x10Convert 6.2x104 4 megameter to nanometer.megameter to nanometer.

Introduction to KinematicsIntroduction to Kinematics

Kinematics is a branch of physics which Kinematics is a branch of physics which deals with the motion of an object without deals with the motion of an object without reference to the forces which act on the reference to the forces which act on the system. (velocity, speed, acceleration, system. (velocity, speed, acceleration, distance, displacement)distance, displacement)

TerminologyTerminology

All quantities in physics are classified All quantities in physics are classified under two categories: vectors and scalars. under two categories: vectors and scalars.

Vector – a quantity that has both Vector – a quantity that has both magnitude magnitude and and direction. direction. Velocity, acceleration, displacement, force. Velocity, acceleration, displacement, force.

Scalar – a quantity that has ONLY Scalar – a quantity that has ONLY magnitude. magnitude. Speed, distance, mass, time.Speed, distance, mass, time.

SituationSituation

Imagine taking a trip to buffalo. Describe some Imagine taking a trip to buffalo. Describe some ways to measure how far you traveled. ways to measure how far you traveled.

Use some system of measurement (feet, inches, Use some system of measurement (feet, inches, meters, furlongs, etc) to determine meters, furlongs, etc) to determine how farhow far you you have traveled.have traveled.

Use some system of measurement to determine Use some system of measurement to determine how far you are from where you started.how far you are from where you started.

Are they the same??Are they the same??

DistanceDistance – is the total length of a path that – is the total length of a path that an object travels.an object travels. Scalar quantity, units meters (m).Scalar quantity, units meters (m).

DisplacementDisplacement – is a change in a position – is a change in a position from its starting point to its end point. from its starting point to its end point. [straight line path]**[straight line path]** Vector quantity, units meters (m).Vector quantity, units meters (m).

Aim: How can we apply the Aim: How can we apply the average velocity formula?average velocity formula?

1)1) List four vectors and scalars.List four vectors and scalars.

2)2) Explain the difference between a vector Explain the difference between a vector and a scalar.and a scalar.

3)3) Dr. House limps 15 meters west then 4 Dr. House limps 15 meters west then 4 meters east then 9 meters west.meters east then 9 meters west.

A) Calculate his total distance traveled.A) Calculate his total distance traveled.

B) Calculate his total displacement. B) Calculate his total displacement.

Speed and VelocitySpeed and Velocity

SpeedSpeed

Units (meters per second) m/sUnits (meters per second) m/s

VelocityVelocity

Units (meter per second) m/sUnits (meter per second) m/s Velocity is a vector!!!!!!Velocity is a vector!!!!!!

t

d

time

cedisv

tan

t

d

time

ntdisplacemev

ExamplesExamples

A car travels between the 50-meter and A car travels between the 50-meter and 150-meter markers on a highway in 10 150-meter markers on a highway in 10 seconds. Calculate the average speed of seconds. Calculate the average speed of the car.the car.

A car travels 100 meters north in 10 A car travels 100 meters north in 10 seconds and then travels 20 meters south seconds and then travels 20 meters south in 2 seconds.in 2 seconds.A) Calculate the average velocity.A) Calculate the average velocity.B) Calculate the average speed.B) Calculate the average speed.C) Compare A and B. C) Compare A and B.

The two average velocity The two average velocity formulas….formulas….

t

dv

2fi vv

v

ExampleExample

A ball starting at rest rolls down a 4 meter A ball starting at rest rolls down a 4 meter ramp. At the end of the ramp the ball’s ramp. At the end of the ramp the ball’s speed is 25 meters per second. Determine speed is 25 meters per second. Determine the average velocity.the average velocity.