Hey, it's Kaleigh and this is our first lesson about forces this lesson is on balanced and unbalanced forces
So what is a force let's start our lesson with a definition a
force is a push or
A pull on an object and sometimes it can even be a twist on an object like wringing out a towel
But there's something else that's very important about forces
There needs to be two objects interacting
So in these pictures you'll see object one is the people
so the person pushing or the two people that are pulling and
They're exerting a force onto a second object in the first picture. It's the
refrigerator that the person is pushing on and
In the second picture, it's the cart full of candy that the people are pulling so they're exerting a force onto a second object
And when the interaction stops when object one is no longer interacting or touching object two
So the person is no longer touching or pushing on the big refrigerator the force no longer exists
Now there are two different types of forces. Do you know what they are?
The first one is contact forces and the other is non-contact forces
some examples of contact forces are
friction or applied forces like a push or a pull and this means two objects are
Physically touching each other to apply the force that's where the interaction is actually touching
but examples of
Non-contact forces are gravity and magnets and this means two objects are still interacting
But they're at a distance from each other and they don't need to be physically touching to apply a force
So in these pictures what kind of force is be applied is it a contact or a non-contact force
Try it's a contact force and that's because they're actually touching each other
So what do you think will happen to the second object?
When the first object is applying a force
so an object one is pushing on the refrigerator or
When the people are pulling on the cart what will happen to the refrigerator in the cart?
The second object will begin to move faster and faster
That means that the object will be
accelerating and
An acceleration is any change to an object's velocity?
So, let's define velocity
Velocity is the speed and direction of an object
so speed is how fast the object is going and
Direction is where the object is going
Let's do an example if
You are walking at 2 meters per second north. Is this your speed or your velocity?
Well, since they tell us that we're going to meters per second and that we're going north
They've given us our speed how fast we're going and our direction
So this is our velocity
Let's try another one if
you are walking at 2 meters per second and
Increase your speed to 5 meters per second. What are you doing?
so they tell us that we
increased our speed so that means were changing our speed and a change to our speed is a change to our
Velocity, so this means we are
accelerating
So in these pictures both carts are
Accelerating and that means the velocity of the carts is changing
Which means that the carts are moving faster and faster
But what's causing them to accelerate what's causing the refridgerator in the cart of candy faster and faster?
They're both experiencing unbalanced forces and that's because the first object that people are
Applying a push or a pull and that's causing
acceleration
Why don't we do a quick lab at home and do some examples about balanced and unbalanced forces
For our balanced forces home experiment you will need yourself and a chair
So you're going to sit on the chair and you're gonna think about these questions
In my changing direction am I changing speed?
What would happen if I experienced an unbalanced force?
What if the floor opened up or the chair broke out from under me?
So, you know the force of gravity is pushing you down into the chair so you can ask yourself. Am I accelerating that?
That would mean that I'm changing
direction and speed
So you can pause the video here sit in the chair and ask yourself these questions
Did you fall through the chair did you fall through the earth
No, you didn't fall through the earth or the chair and that's because the force you are applying to the chair by gravity is
Being met with the force the chair is applying back to you. The forces are
balanced
Now we're going to do an
Unbalanced force experiment so you will need a clean table space and a big book
You're going to begin by pushing very gently on the book and
Then increase the force you are applying to the book until it begins to move
Then you're going to apply even more force and lift your hand off
so you can go ahead and
Pause the video here get your big book and try this experiment
So, let's evaluate what happened
The book didn't slide at first because you pushed the book with a weak force
and it was not enough to overcome the force of friction and
Then you applied enough force that you were able to overcome
friction and the book did move and that means it began to accelerate and then
You shoved the book with enough force that it slid you could lift your hand off and it would keep moving and then it stopped
and
This is because you applied an unbalanced force and that made the book accelerate
but when you stopped the interaction between you in the book the applied force no longer existed and
Friction began to take over and the unbalanced force from friction brought the book to a stop
There was something tricky about the unbalanced forces experiment and it happens when we ask that second question
What happened when I applied enough force to make the book move?
So when you were still pushing on the book
So your hand was on the book and the book was beginning to move
The book may have began to move at a constant speed in the same direction. So
Same speed same direction no acceleration
So what about that force you were applying?
so you were actually applying a balancing force with the friction force and
If the forces are balanced, that means no acceleration
but then you push the book hard enough that you're able to lift your hand up and the book was accelerating and
then friction
became the only applied force and
Started to stop the book from moving which is still an acceleration
Now we're gonna play the net game forces and motion net force together
It's a game of tug-of-war. So first you can watch me play and then you'll be able to play the game on your own
So this is the game net force in the force in forces and motion basics game on the website
You'll see the icon below that you can click after you watch this video to play it on your own
so the first thing
is I have a blue team over here and I have a red team right here and it's a game of tug-of-war and
Whoever wins the game gets this entire cart full of candy
Okay. So, let's see. I'm gonna pick for my blue team. I'm gonna put just this small guy here
I mean for my red team
Let's make it even so I'm gonna put just a small red guy here and I'm gonna click on the speed I con
So I have my speedometer here
and now when I say go
Both of my teams are gonna start pulling and we can watch the speed and see if there's any movement
Because that would mean that there is an unbalanced force. So what happens go?
Well looks like they're pulling and it looks like the speed isn't changing at all. So what does that mean that?
Means they probably have balanced forces, so no acceleration
let's pause and
reset
so now I'm gonna give my blue team a small guy my red team a small guy and
I like the color blue more so I'm gonna give him two and now let's see what happens. So
When I press go, do you think the blue side or the red side is going to have more applied force on the cart?
My bet is on the blue side, but let's see what happens
My speed is increasing so that means I'm accelerating and it's definitely moving towards the blue side and
It looks like blue wins
Nice, let's try it again. So I'm gonna go one small blue guy. How about a big blue guy and
Let's go with the really big red guy
What do you think is gonna happen?
Do you think he won red guy is gonna be able to pull the same amount as these two blue guys
so if it's an unbalanced force one team will win but if it's a balanced force, then the speed won't change and
There won't be any movement. Let's see
Well, my speed still isn't changing so it looks like this one red guy is stronger than both of my blue guys
Let's pause it. Let's give my red guy a little help
Now what will happen?
Do you think he's gonna win the red side or do you think the blue side is gonna win?
Yeah
My speed is changing and I'm having acceleration to the red team
And it looks like red wins
Nice job
So why don't you click the icon below and you can play the game on your own make sure you click the speed icon
So you can see if there's acceleration remember an acceleration is a change of direction
Which would be either going towards the blue side or going towards the red side or if my speedometer changes?
Have fun and remember to always be clever