Momentum and Impulse | Grade 9 Science Quarter 4 Week 3 Lesson

Summary

This engaging video lesson from the Strong Techie YouTube channel dives into the concepts of momentum and impulse, particularly relevant for Grade 9 Science students during Quarter 4, Week 3. The host sets clear learning objectives to examine the effects of collisions and predict related damages or injuries, while also connecting these phenomena to the momentum and impulse of colliding objects. Using relatable examples from basketball and driving scenarios, the video explains momentum as the product of mass and velocity, symbolized as p = m × v. It further explores how changes in velocity, such as those experienced by a bus navigating a curvy road, lead to changes in momentum, which are quantified as impulse. Impulse is defined as the product of force and time of contact, and is crucial in understanding how collisions affect objects. The video also illustrates how the force of impact can be influenced by momentum and contact time, with practical implications such as the design of airbags in cars. Sample problems are solved to demonstrate the calculation of momentum and the determination of force exerted during a football pass. The lesson concludes with scenarios that demonstrate the relationship between impulse and momentum, emphasizing that a greater change in momentum corresponds to a greater impulse. The video is an informative resource for understanding the principles of momentum and impulse in the context of motion and collisions.

Takeaways

• 📚 The concept of momentum is introduced as mass in motion, mathematically expressed as p = m * v, where p is momentum, m is mass, and v is velocity.
• 🏀 Momentum is related to the game of basketball, illustrating how a team's momentum can affect the outcome of a match.
• 🛒 Sample problem solving demonstrates how to calculate the momentum of a moving object, such as a grocery cart.
• 🚫 An object at rest has zero momentum, since velocity is zero.
• 🚌 Real-world scenarios, like a bus on a curvy road, are used to explain changes in velocity and consequently, momentum.
• 📉 A decrease in the mass of a moving object, such as passengers getting off a bus, results in a decrease in momentum.
• 📈 Impulse is defined as the change in momentum, which requires a force to change the momentum of an object.
• ⚖️ Impulse is calculated as the product of force and time (I = F * t), and it's directly proportional to the change in momentum.
• 💥 Collisions, both elastic and inelastic, are a way in which objects can change their momentum.
• 🤾‍♂️ An example of calculating the average force exerted by a player passing a football is provided to illustrate the concept of impulse.
• 🚗 The impact force in a collision is directly proportional to the momentum of the colliding body and inversely proportional to the time of contact.
• 💡 Airbags in cars are designed to extend the time of contact during a collision, thereby reducing the impact force and potentially preventing injuries.

Q & A

What is the main topic of today's video lesson?

Today's video lesson is about momentum and impulse.

What are the two factors that define momentum?

The two factors that define momentum are mass and velocity of an object.

How is momentum mathematically expressed?

Momentum is mathematically expressed as p = m * v, where p is momentum, m is mass, and v is velocity.

What is the unit for momentum?

The unit for momentum is kilogram meter per second (kg·m/s).

What happens to the momentum of an object if it is not moving?

If an object is not moving, its momentum is zero because its velocity is zero.

What is impulse and how is it related to momentum?

Impulse is the change in momentum of a moving object and is equal to the product of force and time. It is the cause of a change in momentum.

How is impulse mathematically expressed?

Impulse is mathematically expressed as I = F * t, where I is impulse, F is force, and t is time.

What is the standard unit for impulse?

The standard unit for impulse is newton second (N·s) or kilogram meter per second (kg·m/s).

How does the time of contact affect the impact force during a collision?

The impact force is inversely proportional to the time of contact. Extending the time of contact can decrease the impact force.

Why are cars designed with airbags?

Cars are designed with airbags to extend the time of contact during a collision, which decreases the impact force and can prevent or lessen injuries.

What is the relationship between impulse and the change in momentum during a collision?

The change in momentum is equal to the impulse experienced by an object. A greater change in momentum results in a greater impulse.

What happens to the mass of objects involved in a collision?

The mass of objects involved in a collision does not change. The change is in their velocity and momentum.

Outlines

00:00

📚 Introduction to Momentum and Impulse

This paragraph introduces the topic of momentum and impulse in the context of a grade 9 science lesson. It sets the learning objectives to examine the effects of collisions and to relate impulse and momentum to the collision of objects. The video encourages students to listen carefully and take notes. It uses basketball as an example to illustrate the concepts, explaining that momentum is the product of mass and velocity (p = m * v). A sample problem is provided to calculate the momentum of a grocery cart, and the concept of zero momentum for a stationary object is discussed. The paragraph also explores what happens to a bus's velocity when it travels on a curvy road and then a straight road, and how the mass of the bus changes when passengers get on and off.

05:01

🏈 Impulse and Its Relation to Momentum

The second paragraph delves into the concept of impulse, which is defined as the change in momentum. It explains that when an object's velocity changes, its momentum changes, and this change is referred to as impulse (i = Δp). Impulse is also described as the product of force and time (i = F * t). A sample problem calculates the average force exerted by an offensive player passing a football, using the given mass, velocity, and time of contact. The paragraph further discusses how the impact force is related to the momentum of the body and the time of contact, using the example of a car crash and airbags to illustrate how extending the time of contact can decrease the impact force.

10:01

💥 Collisions and the Effects on Momentum

The final paragraph provides example scenarios to demonstrate the concept of impulse. It clarifies that an object moving with constant momentum has zero impulse, as there is no change in momentum. The paragraph presents a billiard game scenario to discuss the changes in mass, velocity, and momentum of the cue ball and another ball after a collision. It emphasizes that a change in velocity results in a change in momentum and thus an impulse. Another scenario involving two cars of equal mass colliding is used to show that the car with a greater change in velocity experiences a greater change in momentum and therefore a greater impulse. The paragraph concludes with a recap of the concepts learned and an invitation to continue the discussion in the next video lesson.

Keywords

💡Momentum

Momentum is a measure of the motion of an object, defined as the product of its mass and velocity. In the video, momentum is central to understanding how objects move and interact, especially during collisions. For instance, when a basketball hits a board, its momentum determines the effects of the collision. Mathematically, momentum (p) is expressed as the product of mass (m) and velocity (v), represented as p = m * v.

💡Impulse

Impulse is the change in an object's momentum resulting from a collision or a force applied over a period of time. It is directly related to the force exerted and the duration of the contact. In the video, impulse is used to explain how the force of impact can cause damage, such as in a car crash, and how it can be mitigated by extending the time of contact, like with airbags.

💡Projectile Motion

Projectile motion is the motion of an object thrown or projected into the air, subject to only the acceleration of gravity. It is mentioned in the video as a prerequisite topic, where viewers are assumed to have knowledge of describing motions and the relationship of components of a projectile, which is foundational to understanding momentum and impulse.

💡Collision

A collision is an event in which two or more moving objects come into contact with each other, often resulting in a change of their momentum. The video discusses how collisions can lead to damages or injuries and how understanding momentum and impulse can help predict these outcomes. For example, the change in momentum of a football after being kicked by a player is a direct result of the collision between the player's foot and the ball.

💡Velocity

Velocity is a vector quantity that represents the rate of change of an object's position with respect to time, including both the speed and direction of the object. In the context of the video, velocity is a key component in calculating momentum and understanding the effects of collisions. The change in velocity of a moving bus on a curvy road is used as an example to illustrate the concept.

💡Mass

Mass is a measure of the amount of matter in an object, and it is a scalar quantity. In the video, mass is a fundamental property that, when combined with velocity, determines an object's momentum. The mass of a grocery cart is used in a sample problem to calculate its momentum when it is moving at a certain velocity.

💡Force

Force is an interaction that causes a change in the motion of an object. In the video, force is essential in changing an object's momentum, which is described as the cause of impulse. The average force exerted by a player when kicking a football is calculated using the concept of impulse, demonstrating the direct proportionality between force and the change in momentum.

💡Time of Contact

The time of contact refers to the duration for which two objects are in contact during a collision or an interaction. The video explains that the time of contact can influence the impact force; a longer time of contact can reduce the impact force, which is why car airbags are designed to extend the time of contact during a crash.

💡Elastic and Inelastic Collisions

Elastic and inelastic collisions are two types of collisions with different outcomes regarding the conservation of kinetic energy. In the video, these terms are used to describe how bodies change their momentum through collisions. An elastic collision is one where both momentum and kinetic energy are conserved, while an inelastic collision results in a loss of kinetic energy.

💡Airbags

Airbags are safety devices in vehicles that inflate during a collision to provide a cushion between the passengers and the vehicle's hard surfaces. In the video, airbags are mentioned as an example of how extending the time of contact can reduce the impact force on passengers during a crash, thereby preventing or lessening injuries.

💡Sample Problem

Sample problems are practical examples used in the video to illustrate how to apply the concepts of momentum and impulse to real-world scenarios. They provide a step-by-step approach to solving physics problems, such as calculating the momentum of a moving grocery cart or the force exerted by a player kicking a football.

Highlights

Today's video lesson is about momentum and impulse, and how they relate to collisions of objects.

Momentum is defined as mass times velocity, representing the quantity of motion of an object.

An object with mass that is moving has momentum, while a stationary object has zero momentum.

Impulse is the change in momentum, which occurs when an object's velocity changes due to a force.

Impulse can be calculated as the product of force and the time of contact between two objects.

Bodies change their momentum through collisions, which can be elastic or inelastic.

The impact force of a collision is directly proportional to the momentum of the colliding bodies and inversely proportional to the time of contact.

Cars are designed with airbags to extend the time of contact in a collision, thereby reducing the impact force on occupants.

In a game of billiards, when the cue ball collides with another ball, there is a change in momentum and impulse for both balls.

In a collision between two cars of equal mass, the car with the greater velocity will have a greater change in momentum and impulse.

The video uses examples from basketball and driving scenarios to illustrate the concepts of momentum and impulse.

The video provides a sample problem to calculate the momentum of a moving grocery cart.

The video explains how the mass and velocity of an object determine its momentum.

The video demonstrates how to calculate the average force exerted by a player kicking a football using the concept of impulse.

The video emphasizes that any change in an object's momentum is due to an impulse being applied.

The video discusses how collisions can result in either elastic or inelastic changes in momentum.

The video concludes by summarizing the key concepts of momentum and impulse and their relationship to collisions.

Transcripts

hello students

welcome back to my strong techie youtube

channel

if you haven't watched our video lesson

about projectile motion pause the video

and click the links in the description

box below today's video lesson is a new

topic grade 9 science quarter 4 week 3

lesson is all about momentum and impulse

here's our learning objectives

examine effects and predict causes of

collision related damages or injuries

and relate impulse and momentum to

collision of objects

so what are you waiting for listen

carefully and jot down notes as we learn

about momentum and impulse keep on

watching

[Music]

in the previous topic we talked about

projectile motion at this point you

already know how to describe the motions

and the relationship of the components

of a projectile now let us start with

momentum and impulse suppose you play

basketball with your friends what will

happen to the ball if it hits the board

instead of inside the ring

how about if you bump into another

player that is bigger than you

these questions will be answered as you

go along with this video lesson

one of the most common team sports is

basketball

imagine two teams who are involved in a

really tight tournament quarterfinals

team a has two points ahead of team b

later on in the match

a player from team b scores a three

point shot and followed by a series of

two point shots tim b couldn't stop

their momentum

and what do you mean by momentum

in our example a while ago these are the

things that we need to consider in

defining momentum first the object has a

mass and second the object is moving any

object with a quantity of matter has

momentum and momentum simply means mass

and motion it is equal to the product of

mass and velocity mathematically it is

expressed as p is equal to m times v

where p is the momentum in kilogram

meter per second

m is the mass of the moving object in

kilogram and v refers to the velocity of

the moving object in meter per second

let us try to solve this problem

sample problem 1 what is the momentum of

a 22 kilogram grocery cart which travels

at 1.2 meter per second first let us

have the given the mass of the grossery

cart is 22 kilograms it travels with the

velocity of 1.2 meter per second and we

are looking for the p or the momentum

here's our formula to get the momentum

we need to get the product of mass and

velocity now let us solve this problem

our solution p is equal to the mass

which is 22 kilograms the velocity which

is 1.2 meter per second multiplying

these two the product is

26.4 and the unit is kilogram meter per

second take note how you write the unit

for momentum and this is our final

answer

next

how about the momentum of an object that

is not moving

just like a car that is part

remember class if any object of any mass

is not moving it has zero momentum since

its velocity is zero let us consider

another situation and try to answer the

given questions

suppose you ride a bus from illegal city

to cagayan de oro what do you think will

happen to the bus after it passes along

a curvy road

will it slow down

will it speed up

or the velocity will not change at all

if your answer is letter a

then you are correct

the bus will slow down

if it passes along a curvy road

next question

after passing curvy road the bus travels

in a straight road

how will you describe the velocity of

the bus

it increases

decreases or not change at all

if your answer is letter a

then you are correct

after passing curvy road and travels a

straight road the velocity of the bus

will increase

next

there were only 25 passengers in the bus

along the way four passengers dropped at

lagunding and bus stop and another four

passengers dropped off at oppal bastapp

what can you say about the mass of the

bus it increases

decreases

or not change at all if your answer is

letter b then you are correct the mass

of the bus decreases

based on our example situation we can

say that when the object slows down or

moves faster its velocity decreases or

increases

if there is a change in the velocity of

the mass of an object there is also a

change in momentum and that change of

momentum is what we call

impulse

impulse is equal to the change in

momentum

and it is represented as letter i again

class

impulse is equal to the change in

momentum and remember class that

momentum is equal to the product of mass

and velocity

just like our example there is a change

in momentum and for that to happen force

is needed to change the momentum of a

body this force multiplied by the time

of contact is known as impulse impulse

is equal to the product of force which

is expressed as capital letter f and

time which is expressed as small letter

t analyzing these concepts class we can

say this equation

since impulse is equal to the change of

momentum

and momentum is the product of mass and

velocity

therefore we can say that

impulse is equal to the product of force

and time and mass and velocity the

standard unit for momentum and impulse

is newton second or

kilogram meter per second take note

class bodies change their momentum

through collisions which may be elastic

or inelastic let us have a sample

problem

sample problem number two an offensive

player passes a football of mass 0.42

kilogram with a velocity of

25.0 meter per second due south if the

player is in contact with the ball for

0.050 seconds what is the magnitude of

the average force he exerts

here are the given for our problem

the mass of the ball is 0.42 kilogram

its velocity is 25.0 meter per second

south

and the time contact with the ball is

0.050 seconds and we are looking for the

force remember class our formula for the

impulse impulse is equal to the product

of force and time which is also equal to

the product of mass and velocity since

we need to determine the force we can do

some algebra with this equation using

division property of equality let us

divide d both sides and we can cancel

out time on the left side of the

equation therefore we can get this

formula force is equal to the product of

mass and velocity divided by time now

let us solve this problem

for our solution let us substitute our

given to our formula force is equal to

the mass which is 0.42 kilogram

our velocity which is 25.0 meter per

second

all over our time which is 0.050

second

0.42 times

25.0 we have

10.5 in our unit kilogram meter per

second

divided by 0.050

seconds

dividing these the quotient will be

210 kilogram meter per second squared

and this is our final answer and that is

how you solve this kind of problem

rearranging our equation will help us

understand how impact force is affected

by the change in momentum and the time

of contact it shows that the force of

impact is directly proportional to the

momentum of the body and inversely

proportional to the time of contact we

can say for example that the impact

force of a fast moving car is higher and

therefore it can cause greater damage

after the collision than the car moving

at a lower velocity on the other hand

the equation also tells us that the

impact force could be decreased by

extending the time of contact that is

why cars are designed with air bugs

because it can lessen or prevent

injuries in the event of crash or

collision the inflation of the airbag is

initiated by crash sensors these

decreases the impact force by increasing

the time of contact next let's have some

example scenarios exhibiting impulse

what do you think is the impulse of an

object moving with constant momentum

constant means no change at all

therefore there is no impulse or zero

impulse for objects moving with constant

momentum take note of that class you now

know

that any object has momentum and it is

equal to the product of mass and

velocity

impulse on the other hand is a change of

momentum of a moving object next

what will happen to a moving object if

it collides with another object let's

have this scenario suppose you are

playing billiard

the cue ball and ball number one are

initially at rest

then you use the taco to hit ball number

one based on the given illustration

answer the following questions

what did you observe on the mass of the

cue ball before and after collision

there is no change in mass how about

ball number one

also there is no change in their mass

question number two

since it is initially at rest what are

the initial velocity of the balls

the answer

zero question number three

after collision is there a change in

velocity of the cue ball and ball number

one

the answer

yes

question number four

is there a change in momentum

of the cue ball and ball number one

and why

since there is a change in the velocity

of course there is a change in momentum

therefore

there is impulse

because there is a change in momentum

since the cue ball and ball number one

have a change in velocity after

collision then

both balls have a change in momentum

also in collisions an object that

experiences a greater change in momentum

has greater impulse

therefore this shows the relationship

between impulse and momentum that a

change in momentum is equal to impulse

let's have another scenario suppose that

two cars with equal masses collide with

each other car a travels faster than car

b

they both stop after collision note that

the bigger the letter of velocity or

mass the greater its value and in this

scenario the greater velocity is car a

now

given this scenario which of the two

cars has the greater change of velocity

the answer is car a

next

which car has the greater change in

momentum

explain your answer

the answer

car a because it travels faster than car

b therefore it has greater velocity

remember class greater velocity means

greater change in momentum next question

which car has the greater impulse

the answer is car a because it has

greater change in momentum in other

words the object that experience a

greater impulse is the one that has the

greater change in momentum and that ends

our lesson about impulse and momentum i

hope you learned something new and you

take note the concepts about impulse and

momentum we will continue discussing

this topic in our next video lesson so

to keep you posted do not forget to like

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[Music]

you