WEBVTT
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Okay, wait.
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You're sitting in a chair right now, right?
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Maybe you're sitting at your desk.
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Maybe you're sitting on the couch.
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Maybe you're supposed to be sitting down, but somehow you're wandering around the room looking for a pencil you've already borrowed three times today.
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Either way, something is happening to you right now.
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Gravity is pulling you down.
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And if you're sitting in a chair, the chair is pushing you up.
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Wait.
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So you're telling me there is an entire invisible battle happening between you, Earth, and your chair?
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And you're just sitting there?
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Oh baby.
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Wait, that's science.
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Welcome back to Wait That's Science with Dr.
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Rodriguez, where we uncover the science hiding in everyday life.
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This week we're talking about forces.
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A force is simply a push or a pull, and forces are everywhere.
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Push your Chromebook across your desk, force.
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Kick a soccer ball, force.
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Pull it open a door.
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Force.
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Drop your phone.
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First of all, I hope you have a case.
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Second, gravity.
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But here's where it gets interesting.
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Not every force works the same way.
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Some forces require objects to actually touch each other.
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We call those contact forces.
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Other forces can act on an object without touching it.
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Those are non-contact forces.
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So today we're investigating five forces you need to know.
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Applied force, friction, normal force, gravity, and magnetism.
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Big word easy meaning.
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Let's start with applied force.
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Big word easy meaning.
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An applied force happens when a person or another object pushes or pulls something.
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If I push a chair under my desk, I am applying a force.
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If you pull your backpack off the floor, applied force.
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If somebody pushes their desk three feet across my classroom for absolutely no reason, applied force.
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Unnecessary, applied force, but applied force nonetheless.
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And because the objects have to interact directly, applied force is a contact force.
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Friction.
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Now let's say I push a book across a table.
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Eventually the book slows down and stops.
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Why?
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Friction.
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Friction is a force that opposes motion when surfaces rub against each other.
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And before you decide friction is the villain of the story, understand that we need friction.
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Imagine trying to walk down the hallway with absolutely no friction between your shoes and the floor.
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You take one step and whee! You're sliding past the cafeteria.
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Friction helps your shoes grip the ground.
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It helps bicycle brakes work.
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It helps tires grip the road.
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So friction can slow things down, but it can also help us control motion.
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And because the surfaces have to touch, you guessed it.
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Contact force.
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Normal force.
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Okay, this next one has a name that makes it sound way more complicated than it is.
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Normal force.
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Remember that chair you were sitting in?
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Gravity is pulling you downward, but you're not falling through the chair.
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Why?
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Because the chair is pushing back up on you.
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That supporting push from a surface is called the normal force.
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Put a book on a table.
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Gravity pulls the book down.
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The table pushes up on the book.
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Normal force.
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Stand on the floor.
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Gravity pulls you down.
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The floor pushes up.
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Normal force.
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So yes, the floor is literally supporting you.
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Tell the floor thank you.
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Time for weight, is that true?
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Here's today's statement.
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If an object is not moving, there are no forces acting on it.
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Is that true?
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Nope.
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Think about our book sitting on the table.
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The book may not be moving, but gravity is still pulling it downward while the table provides an upward normal force.
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Forces can act on an object even when the object isn't moving.
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That's important.
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Gravity.
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Now we're moving into our non-contact forces.
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First up, gravity.
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Gravity is an attractive force between objects with mass.
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Earth's gravity pulls objects toward Earth.
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Drop your pencil, gravity.
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Jump into the air and come back down.
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Gravity.
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Drop your water bottle for the fourth time during class.
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Gravity.
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Although at some point, we also need to discuss why the water bottle keeps leaving your desk.
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The important part is this.
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Earth does not need to physically touch you to pull you toward it.
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That makes gravity a non-contact force.
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Magnetism.
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No other non-contact force.
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Pardon me.
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Our other non-contact force is magnetism.
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You've probably seen magnets attract certain materials without touching them first.
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Bring two magnets close together, and depending on which poles are facing each other, they may attract or repel.
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That means an object can experience a push or pull without direct contact.
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And that is why magnetism is another non-contact force.
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Okay, Toros, turn and tell somebody near you what forces are acting on you right now.
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Think about it.
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Are you sitting in a chair, standing on the floor, holding something?
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Did you just slide your notebook across your desk?
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Use the sentence stem.
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One force acting on me or an object near me is I know because and I want more than gravity because gravity.
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Absolutely not.
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Give me the science.
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Let's see what you know.
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I'll give you a situation.
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You name the force.
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Ready?
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Situation number one.
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You push open the classroom door.
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That push is an applied force.
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Next.
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Your shoe grips the basketball court instead of sliding everywhere.
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Good job.
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It's friction.
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Next.
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A book rests on your desk and the desk pushes upward on it.
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Normal force.
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Next.
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You toss a ball into the air and it comes back down.
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Gravity.
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Last one.
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A magnet pulls a metal object toward it without touching it first.
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Magnetism.
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Okay.
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Now, one more level.
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Which three of those are contact forces?
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Applied force?
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Friction?
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Normal force.
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And which two are non-contact forces?
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Gravity?
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Magnetism?
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There it is.
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Here's your challenge for this week.
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Become a force detective.
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Pick one everyday situation.
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Maybe you're riding in a car, playing basketball, opening your locker, walking down the hallway, sitting at your desk, or carrying your backpack.
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Identify at least two forces acting in that situation.
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Then tell me whether each force is a contact force or a non-contact force.
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But don't stop there.
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Explain how you know, because scientists don't just name things.
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Scientists use evidence to explain their thinking.
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Before you go, here's your exit question.
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A student says, if I'm sitting completely still in my chair, no forces are acting on me.
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Do you agree or disagree?
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Explain your answer using the words gravity and normal force.
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Sentence den I with the student because gravity, while the normal force.
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If you can explain that, you understand something pretty cool.
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Steel does not mean force free.
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So the next time you push a door, slide across the floor, drop your pencil, sit in a chair, or stick something to a magnet.
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I want that little science voice in your head to say, wait, that's science.
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Because forces aren't just something hiding in your textbook.
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They are pushing, pulling, attracting, resisting, and supporting objects around you all day long.
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I'm Dr.
00:11:44.080 --> 00:11:48.960
Rodriguez and this has been Wait That's Science.
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Remember, stay curious, keep asking why, and never stop looking for the science hiding in everyday life.
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Wait That Science is produced by Godsey Media and Consulting.
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Okay, wait.
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You're sitting in a chair right now, right?
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Maybe you're sitting at your desk.
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Maybe you're sitting on the couch.
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Maybe you're supposed to be sitting down, but somehow you're wandering around the room looking for a pencil you've already borrowed three times today.
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Either way, something is happening to you right now.
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Gravity is pulling you down.
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And if you're sitting in a chair, the chair is pushing you up.
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Wait.
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So you're telling me there is an entire invisible battle happening between you, Earth, and your chair?
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And you're just sitting there?
00:00:50.240 --> 00:00:51.679
Oh baby.
00:00:52.479 --> 00:00:55.359
Wait, that's science.
00:00:56.399 --> 00:00:59.359
Welcome back to Wait That's Science with Dr.
00:00:59.520 --> 00:01:04.400
Rodriguez, where we uncover the science hiding in everyday life.
00:01:04.719 --> 00:01:07.680
This week we're talking about forces.
00:01:09.040 --> 00:01:14.799
A force is simply a push or a pull, and forces are everywhere.
00:01:15.040 --> 00:01:18.640
Push your Chromebook across your desk, force.
00:01:19.120 --> 00:01:21.920
Kick a soccer ball, force.
00:01:22.480 --> 00:01:24.560
Pull it open a door.
00:01:25.200 --> 00:01:25.840
Force.
00:01:26.560 --> 00:01:28.319
Drop your phone.
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First of all, I hope you have a case.
00:01:32.159 --> 00:01:34.480
Second, gravity.
00:01:35.280 --> 00:01:37.840
But here's where it gets interesting.
00:01:38.159 --> 00:01:40.719
Not every force works the same way.
00:01:41.519 --> 00:01:45.439
Some forces require objects to actually touch each other.
00:01:45.680 --> 00:01:48.159
We call those contact forces.
00:01:48.640 --> 00:01:52.719
Other forces can act on an object without touching it.
00:01:53.040 --> 00:01:55.599
Those are non-contact forces.
00:01:56.079 --> 00:02:00.719
So today we're investigating five forces you need to know.
00:02:01.200 --> 00:02:09.199
Applied force, friction, normal force, gravity, and magnetism.
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Big word easy meaning.
00:02:13.120 --> 00:02:15.520
Let's start with applied force.
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Big word easy meaning.
00:02:18.960 --> 00:02:25.520
An applied force happens when a person or another object pushes or pulls something.
00:02:26.080 --> 00:02:31.120
If I push a chair under my desk, I am applying a force.
00:02:31.360 --> 00:02:36.159
If you pull your backpack off the floor, applied force.
00:02:36.879 --> 00:02:45.039
If somebody pushes their desk three feet across my classroom for absolutely no reason, applied force.
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Unnecessary, applied force, but applied force nonetheless.
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And because the objects have to interact directly, applied force is a contact force.
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Friction.
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Now let's say I push a book across a table.
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Eventually the book slows down and stops.
00:03:08.159 --> 00:03:08.800
Why?
00:03:10.080 --> 00:03:11.039
Friction.
00:03:11.759 --> 00:03:17.280
Friction is a force that opposes motion when surfaces rub against each other.
00:03:17.680 --> 00:03:23.919
And before you decide friction is the villain of the story, understand that we need friction.
00:03:24.800 --> 00:03:31.919
Imagine trying to walk down the hallway with absolutely no friction between your shoes and the floor.
00:03:32.240 --> 00:03:39.520
You take one step and whee! You're sliding past the cafeteria.
00:03:40.080 --> 00:03:43.280
Friction helps your shoes grip the ground.
00:03:43.599 --> 00:03:46.159
It helps bicycle brakes work.
00:03:46.639 --> 00:03:49.439
It helps tires grip the road.
00:03:49.759 --> 00:03:55.520
So friction can slow things down, but it can also help us control motion.
00:03:56.560 --> 00:04:00.960
And because the surfaces have to touch, you guessed it.
00:04:01.280 --> 00:04:02.879
Contact force.
00:04:03.919 --> 00:04:05.199
Normal force.
00:04:05.520 --> 00:04:11.280
Okay, this next one has a name that makes it sound way more complicated than it is.
00:04:11.680 --> 00:04:13.039
Normal force.
00:04:13.360 --> 00:04:15.840
Remember that chair you were sitting in?
00:04:16.480 --> 00:04:21.439
Gravity is pulling you downward, but you're not falling through the chair.
00:04:21.759 --> 00:04:22.399
Why?
00:04:23.279 --> 00:04:26.240
Because the chair is pushing back up on you.
00:04:26.800 --> 00:04:31.759
That supporting push from a surface is called the normal force.
00:04:32.079 --> 00:04:33.920
Put a book on a table.
00:04:34.240 --> 00:04:36.240
Gravity pulls the book down.
00:04:36.560 --> 00:04:38.959
The table pushes up on the book.
00:04:39.279 --> 00:04:40.560
Normal force.
00:04:41.120 --> 00:04:42.879
Stand on the floor.
00:04:43.519 --> 00:04:45.360
Gravity pulls you down.
00:04:45.759 --> 00:04:47.759
The floor pushes up.
00:04:48.399 --> 00:04:49.680
Normal force.
00:04:50.160 --> 00:04:54.240
So yes, the floor is literally supporting you.
00:04:54.560 --> 00:04:56.560
Tell the floor thank you.
00:04:58.000 --> 00:05:00.959
Time for weight, is that true?
00:05:02.399 --> 00:05:04.319
Here's today's statement.
00:05:04.720 --> 00:05:09.680
If an object is not moving, there are no forces acting on it.
00:05:10.160 --> 00:05:11.439
Is that true?
00:05:12.800 --> 00:05:13.759
Nope.
00:05:14.399 --> 00:05:17.120
Think about our book sitting on the table.
00:05:17.439 --> 00:05:26.000
The book may not be moving, but gravity is still pulling it downward while the table provides an upward normal force.
00:05:26.560 --> 00:05:31.360
Forces can act on an object even when the object isn't moving.
00:05:31.839 --> 00:05:32.959
That's important.
00:05:34.319 --> 00:05:35.199
Gravity.
00:05:35.519 --> 00:05:38.879
Now we're moving into our non-contact forces.
00:05:39.279 --> 00:05:41.439
First up, gravity.
00:05:42.160 --> 00:05:46.319
Gravity is an attractive force between objects with mass.
00:05:46.879 --> 00:05:50.240
Earth's gravity pulls objects toward Earth.
00:05:50.480 --> 00:05:53.519
Drop your pencil, gravity.
00:05:54.000 --> 00:05:56.399
Jump into the air and come back down.
00:05:57.519 --> 00:05:58.399
Gravity.
00:05:59.120 --> 00:06:02.720
Drop your water bottle for the fourth time during class.
00:06:03.839 --> 00:06:04.720
Gravity.
00:06:05.680 --> 00:06:12.240
Although at some point, we also need to discuss why the water bottle keeps leaving your desk.
00:06:12.959 --> 00:06:15.120
The important part is this.
00:06:15.759 --> 00:06:20.480
Earth does not need to physically touch you to pull you toward it.
00:06:20.720 --> 00:06:24.079
That makes gravity a non-contact force.
00:06:25.120 --> 00:06:26.240
Magnetism.
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No other non-contact force.
00:06:30.720 --> 00:06:31.920
Pardon me.
00:06:33.120 --> 00:06:36.959
Our other non-contact force is magnetism.
00:06:37.920 --> 00:06:43.040
You've probably seen magnets attract certain materials without touching them first.
00:06:43.680 --> 00:06:51.839
Bring two magnets close together, and depending on which poles are facing each other, they may attract or repel.
00:06:52.720 --> 00:06:58.560
That means an object can experience a push or pull without direct contact.
00:06:58.800 --> 00:07:03.040
And that is why magnetism is another non-contact force.
00:07:04.480 --> 00:07:12.000
Okay, Toros, turn and tell somebody near you what forces are acting on you right now.
00:07:12.399 --> 00:07:13.680
Think about it.
00:07:13.920 --> 00:07:20.480
Are you sitting in a chair, standing on the floor, holding something?
00:07:21.519 --> 00:07:24.639
Did you just slide your notebook across your desk?
00:07:25.519 --> 00:07:27.439
Use the sentence stem.
00:07:28.480 --> 00:07:44.000
One force acting on me or an object near me is I know because and I want more than gravity because gravity.
00:07:45.040 --> 00:07:46.399
Absolutely not.
00:07:46.800 --> 00:07:48.560
Give me the science.
00:07:50.000 --> 00:07:51.680
Let's see what you know.
00:07:52.079 --> 00:07:53.920
I'll give you a situation.
00:07:54.399 --> 00:07:56.079
You name the force.
00:07:56.720 --> 00:07:57.360
Ready?
00:07:59.199 --> 00:08:01.040
Situation number one.
00:08:01.600 --> 00:08:04.000
You push open the classroom door.
00:08:04.480 --> 00:08:10.879
That push is an applied force.
00:08:13.199 --> 00:08:13.839
Next.
00:08:14.959 --> 00:08:22.560
Your shoe grips the basketball court instead of sliding everywhere.
00:08:26.959 --> 00:08:27.839
Good job.
00:08:28.000 --> 00:08:29.199
It's friction.
00:08:30.079 --> 00:08:30.720
Next.
00:08:31.600 --> 00:08:36.240
A book rests on your desk and the desk pushes upward on it.
00:08:39.440 --> 00:08:40.960
Normal force.
00:08:42.000 --> 00:08:42.639
Next.
00:08:43.840 --> 00:08:47.600
You toss a ball into the air and it comes back down.
00:08:50.399 --> 00:08:51.360
Gravity.
00:08:52.639 --> 00:08:53.600
Last one.
00:08:54.559 --> 00:08:59.360
A magnet pulls a metal object toward it without touching it first.
00:09:01.440 --> 00:09:02.559
Magnetism.
00:09:04.000 --> 00:09:04.320
Okay.
00:09:06.000 --> 00:09:08.639
Now, one more level.
00:09:09.360 --> 00:09:12.399
Which three of those are contact forces?
00:09:13.360 --> 00:09:14.960
Applied force?
00:09:15.440 --> 00:09:16.399
Friction?
00:09:17.120 --> 00:09:18.639
Normal force.
00:09:21.840 --> 00:09:25.519
And which two are non-contact forces?
00:09:26.159 --> 00:09:27.039
Gravity?
00:09:27.919 --> 00:09:29.039
Magnetism?
00:09:32.720 --> 00:09:33.919
There it is.
00:09:36.559 --> 00:09:39.039
Here's your challenge for this week.
00:09:39.759 --> 00:09:42.159
Become a force detective.
00:09:42.559 --> 00:09:44.799
Pick one everyday situation.
00:09:45.279 --> 00:09:58.399
Maybe you're riding in a car, playing basketball, opening your locker, walking down the hallway, sitting at your desk, or carrying your backpack.
00:09:58.960 --> 00:10:03.840
Identify at least two forces acting in that situation.
00:10:04.399 --> 00:10:10.559
Then tell me whether each force is a contact force or a non-contact force.
00:10:10.879 --> 00:10:12.320
But don't stop there.
00:10:12.960 --> 00:10:18.639
Explain how you know, because scientists don't just name things.
00:10:18.960 --> 00:10:22.480
Scientists use evidence to explain their thinking.
00:10:23.919 --> 00:10:27.679
Before you go, here's your exit question.
00:10:28.000 --> 00:10:36.159
A student says, if I'm sitting completely still in my chair, no forces are acting on me.
00:10:37.200 --> 00:10:40.240
Do you agree or disagree?
00:10:42.320 --> 00:10:48.240
Explain your answer using the words gravity and normal force.
00:10:49.600 --> 00:11:00.159
Sentence den I with the student because gravity, while the normal force.
00:11:03.039 --> 00:11:07.759
If you can explain that, you understand something pretty cool.
00:11:08.080 --> 00:11:10.720
Steel does not mean force free.
00:11:11.679 --> 00:11:21.759
So the next time you push a door, slide across the floor, drop your pencil, sit in a chair, or stick something to a magnet.
00:11:22.720 --> 00:11:29.759
I want that little science voice in your head to say, wait, that's science.
00:11:30.320 --> 00:11:33.840
Because forces aren't just something hiding in your textbook.
00:11:34.000 --> 00:11:42.399
They are pushing, pulling, attracting, resisting, and supporting objects around you all day long.
00:11:43.200 --> 00:11:43.919
I'm Dr.
00:11:44.080 --> 00:11:48.960
Rodriguez and this has been Wait That's Science.
00:11:49.600 --> 00:11:59.600
Remember, stay curious, keep asking why, and never stop looking for the science hiding in everyday life.
00:12:00.960 --> 00:12:06.799
Wait That Science is produced by Godsey Media and Consulting.
