Motion basics

Chapter 1

Mr. Whitney

Sign Convention & Direction

Motion has a 1) Direction2) Magnitude - How much motion has or is occurring

Positive: Up, to the right, North, to the EastNegative: Down, to the left, South, to the West

Sign Convention & Direction

Motion has a 1) Direction2) Magnitude Needs a frame of reference, an origin to definepositions at different times.

Requires changes in TIMEUniform Motion means a time intervals are the same

Distance & Displacement

Distance (x) equates

Displacement equates to Difference between initial xi and final xf .

x is position from the reference

Displacement

Displacement is written:

A person moves on the number line shown below. The person begins at B, walks to C, and then turns around and walks to A. For this entire range of motion DETERMINE: a)the person’s final positionb)the displacementc)the distance.

Example

0 5 m 10 m 15 m

A B C

Speed & Velocity

Speed: How far

Velocity: How

Speed: distance traveled time interval

Speed and Direction

Velocity = x t

Average Speed & Velocity

EXAMPLEUsain Bolt holds the record for the 100m sprint completing it in only 9.58s!

a) Determine his average speed in m/s. (1.6km = 1mi)

b) Mr Sample (I hold no record) ran the Philly half-marathon (13.1mi) in 1hr55min36sec. Determine my avg speed in mph.

Did he run faster than this at some point?

Vectors

Go East then go West

What is the final displacement? (this is

a vector)

What is the distance traveled?

5 mi 3 mi

Vectors

Go East then go South

What is the final displacement? (this is

a vector)

What is the distance traveled?

4 mi 3 mi

Vector Notation

• Vector A A

• A + B This adds the 2 vectors

• Vectors do not have to be in the same

Direction to be added.

See page 19 in textbook

Vectors and Trig

Were A, B, and C are vectors (magnitude and direction)

•sin Θ = A/C

•cos Θ = B/C

•tan Θ = A/B

Describing Motion:

Kinematics in One Dimension

A commuter drives 15.0km on the highway at a speed of 25.0m/s, parks at work and walks 150m at a speed of 1.50m/s from his car to his office.

Example

b) Determine the average speed of the entire commute

(a) Determine the total time of the commute.

Example: A woman starts at the entrance to a mall and walks inside for 185m north for 10minutes. She then walks 59m south in 3minutes to another store. She then leaves the store and moves south 155m in 8minutes to reach her car outside.Determine her average velocity during the trip.

Instantaneous Velocity

The instantaneous speed or velocity is how fast an object is moving at a single point in time.

Does the gauge on your dashboard give you speed or velocity?

Does this gauge give you an average or instantaneous value?