Velocity and momentum

Velocity and Momentum

Lesson 2

U1- M2 –L2

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MODULE 2 Motion:

1- Describing Motion ……………………………..38-44

2-Velocity and Momentum........................ 45-49

3 -Acceleration ……………….......................... 50-54

Grade 9 General

How does the velocity of an object affect its
momentum?

Focus Question

momentum

velocity

New Vocabulary

speed: rate of change of position

Review Vocabulary

90 km /h
90 km/h west

What is different between

2

pictures??

•

Velocity includes the speed of an object and
the direction of its motion.

•

Velocity has the same units as speed, m/s.

•

Because velocity depends on the direction as
well as speed, the velocity of an object can
change even if the speed of the object
remains constant.

•

It is possible for two objects to have the same
speed but different velocities.

Velocity

• Velocity includes the speed of an object

and the direction of its motion.

Velocity

•

Velocity has the same units as speed, m/s.

Velocity

Look at the
following picture
and tell ..
What we mean by
velocity??

Two objects can have the:

1-same speeds,

2-but different velocities.

Explore

Because velocity depends on the direction as well as
speed, the velocity of an object can change even if the
speed of the object remains constant.

The cars on both sides have same ----------
,but different ----------------------.

60

60

The cars on both sides have same Speed

,but different Velocity

60

60

•

It is possible for two objects to have the same speed but
different velocities.

Velocity

* Explain:

It is possible for two objects to have the same speed

but different velocity

For example, two cars are moving
60Km/hr. , but one is moving north
and other south

• Speed is the distance an object travels

per unit of time

Velocity

• Velocity includes the speed of an

object and the direction of its motion.

• Answer the worksheet:-

Comparison

Speed

Velocity

Definition

describes only how fast

something is moving.

includes the speed of an

object and the direction of

its motion

Depending on

direction

Does not depend

Depends

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•

The basic structure of the surface of Earth
seems to stay the same from year to year.

•

Yet, geologic evidence of what the surface
looked like over the past 250 million years
shows that large changes have occurred.

•

According to the theory of plate tectonics, the
positions of landmasses have changed as
shown below. Changes in the landscape occur
constantly as continents drift slowly over
Earth’s surface.

Motion of Earth’s Crust

Plate tectonics is a theory that explains the structure

of the Earth’s crust.

The crust is broken up into many tectonic plates.
Each plate only moves a few centimeters per year.

Plate Tectonics

​These moving plates cause geologic changes:

1. formation of mountain ranges

2. earth quakes

3. volcanic eruptions

4. size of oceans

   pacific ocean --> smaller

   Atlantic ocean --> Larger

5. Shape of continents

Relative Motion

•

The choice of a moving reference point affects how you
describe motion.

•

For example, the motion of a hurricane can be
described using a stationary reference point, such as a
house.

Relative Motion

Relative Motion

The distance between the hurricane and the house is
decreasing at a rate of 20 km/h.

The distance between the house and the car is increasing
at a rate of 10 km/h.

•

The figures on the next slide show the locations and
velocities of a hurricane and a car relative to a house at
different times.

•

•

Relative Motion

If the car is chosen for the reference point, the
house appears to be traveling 10 km/h east and
the hurricane appears to be traveling 10 km/h
west.

Relative Motion

•

A useful way of describing both the velocity and mass
of an object is to state its momentum.

•

The momentum of an object is the product of its mass
and velocity. Momentum is usually represented by the
symbol p.

Momentum Equation
momentum (in kg⋅m/s) = mass (in kg) × velocity (in m/s)

𝜌=mv

Momentum

Momentum

Effect of Mass

Effect of velocity

Any object have velocity will have momentum

•Which ball will move the box
more ?

•High or low velocity
will move the box
more?

the child on the tricycle would be easier to stop. But why?

Apply

It would be easier to stop the child because he has less mass

than the train.

Apply

• The momentum of an

object is the product of

its mass and velocity.

Which has the largest Momentum??

30 m/s east

30 m/s east

1800 kg

25000 kg

Which has the largest Momentum??

30 m/s east

1800 kg

1800 kg

40 m/s east

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•Solve the work sheet

•

Multiple Choice

Both the beetle , the bike and the car have the same velocity ,

which has less momentum?

Not all things move fast.
Compare pouring water into a glass to pouring maple syrup
on pancakes.

Velocity is independent of direction.

D

Velocity describes how fast an object is changing
speed.

C

The velocity of an object can change even if the
speed of the object remains constant.

B

Two objects with the same speed always have the same
velocity.

A

Which of the following is true?

2.

CORRECT

Quiz

A small object moving at the same speed as larger
object will have less momentum.

D

An object’s momentum is always in the same
direction as its velocity.

C

It is the product of an object’s speed and
velocity.

B

It has a size and a direction.

A

Which of the following is NOT true of
momentum?

5.

CORRECT

Quiz

Multiple Choice

Which describes velocity?

• The product of mass and speed.

• The instantaneous speed.

• The rate in which speed changes.

• The speed of an object and the direction of its motion.

Multiple Choice

Which of the following is true?

• Two objects with the same speed always have the same velocity.

• The velocity of an object can change even if the speed of the object remains constant.

• Velocity describes how fast an object is changing speed.

• Velocity is independent of direction.

Multiple Choice

Which of the following statements is NOT true?

• Geologic evidence suggests Earth’s crust is changing.

• The choice of a moving reference point affects how you describe motion.

• An elevator moving up at 2 m/s has the same velocity as an elevator moving down at 2 m/s.

• Velocity and position always depend on the point of reference chosen

Multiple Choice

What is the momentum of a 1000-kg car that is driving 60 m/s east?

• 60,000 kg·m/s east

• 1.67 kg·m/s east

• 16.7 kg·m/s east

• 0.167 kg·m/s east

Multiple Choice

Which of the following is NOT true of momentum?

• It has a size and a direction.

• It is the product of an object’s speed and velocity.

• An object’s momentum is always in the same direction as its velocity.

• A small object moving at the same speed as larger object will have less momentum.