Physics L2 www.slideshare.net/DMS_physics

Motion is relative Motion = change in position of an object System of Reference

Motion = change in position of an object

System of Reference

Speed A measure of how fast something is moving (see p.12) Average speed is the total distance divided by the time interval

A measure of how fast something is moving (see p.12)

Average speed is the total distance divided by the time interval

Instantaneous speed A measure of how fast an object is moving at a certain time speedometer odometer

A measure of how fast an object is moving at a certain time

speedometer

odometer

Over to you P.13 / Q.1 P.13 / Q.2

P.13 / Q.1

P.13 / Q.2

Velocity has speed and direction

has speed and direction

Scalars and Vectors Scalars = have only one value Ex: time, speed, temperature Vectors = have two or three values (magnitude and direction) Ex: velocity, force, acceleration

Scalars = have only one value

Ex: time, speed, temperature

Vectors = have two or three values (magnitude and direction)

Ex: velocity, force, acceleration

Over to you (p.14/Q) The speedometer of a car moving northward reads 60 km/h. It passes another car that travels southward at 60 km/h. Do both cars have the same speed? Do they have the same velocity?

The speedometer of a car moving northward reads 60 km/h. It passes another car that travels southward at 60 km/h.

Do both cars have the same speed?

Do they have the same velocity?

Constant and changing velocity Constant velocity both speed and direction are constant The motion occurs in a straight line Uniform (linear) motion Changing velocity Either one of speed or direction are changing, or both

Constant velocity

both speed and direction are constant

The motion occurs in a straight line

Uniform (linear) motion

Changing velocity

Either one of speed or direction are changing, or both

Over to you Q: What controls are used to change velocity in a car?

Q: What controls are used to change velocity in a car?

Over to you A: gas pedal, brake, steering wheel

A: gas pedal, brake, steering wheel

Acceleration Is the rate at which velocity is changing Acceleration is a vector

Is the rate at which velocity is changing

Acceleration is a vector

Uniform Circular Motion Speed is constant Velocity is changing Acceleration points towards the center of the motion

Speed is constant

Velocity is changing

Acceleration points towards the center of the motion

Classwork Consider a car that is leaving drops of oil on the road. Show how the drops would look if The car is traveling at constant velocity The car is accelerating (increasing its velocity) The car is decelerating (reducing its velocity)

Consider a car that is leaving drops of oil on the road. Show how the drops would look if

The car is traveling at constant velocity

The car is accelerating (increasing its velocity)

The car is decelerating (reducing its velocity)

Answer Constant speed (zero acceleration) Positive acceleration (accelerating) Negative acceleration (decelerating)

Example (p.16/Q1) Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration? Answer:

Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration?

Answer:

Classwork P.16 / Q2 In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vehicle?

P.16 / Q2

In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vehicle?

Homework assignment P. 25 / 12 What is the acceleration of a car moving along a straight-line path that increases its speed from 0 to 100 km/h in 10s ?

P. 25 / 12

What is the acceleration of a car moving along a straight-line path that increases its speed from 0 to 100 km/h in 10s ?

Homework assignment P. 25 / 13 By how much does the speed of a vehicle moving in a straight line change each second when it is accelerating at 2 km/h.s?

P. 25 / 13

By how much does the speed of a vehicle moving in a straight line change each second when it is accelerating at 2 km/h.s?

End L2