What is a Force?

Force is a central concept in physics. By analysing the forces on an object, its resulting motion can be determined. But what exactly is a force? The word force is used in everyday language in a variety of contexts, only some of which reflect the scientific definition of force. In this video, people at Victoria Park in Sydney are interviewed on their ideas of force and the forces that act on them.

[sharank]

you know this guy's philosophy actually works. Even i thought that gravity is the only force acting in the beginning in the beginning. But then when he started asking if there are any other forces i started remebering physics lessons in my school. kudos to your philosophy, Derek!

[VinaXR]

those older videos of yours are very cool, simple but informative. I've never seen them before, must be that new youtube algorithm coz they pop up in my recommendations

[scottfrazier]

Thank you for making this video. As a high school Physics teacher, I can tell you this works great to get students thinking... and to start a lot of discussion around free body diagrams and analysis of systems. Wonderful job!

[JandCanO]

1:08 I hate when people start trying to sound smart when they really have no clue what they are talking about.

[arminnieuseeberger]

I love watching these videos, they make me feel like a genius

[aizadsyaiful]

when standing up. we have :-
- gravitational pull which pull us down to the center of the earth.
- atmospheric pressure. a push (1atm)
- and a normal reaction force which is a push on an opposite direction of gravitational pull. - this force is important because it will make the resultant force, F = 0. so we can stand still.
-and maybe some friction which is a pull. if i was shaking or fidgeting or moving

[veritasium]

@Tossphate Yeah, I'm getting around to the 4 force video (or 3 or 5 depending on how you want to look at it). I know it's been awhile but I've got distracted with other things. Why can't you walk through walls is one I'd like to do...

[loudandlearnt]

I've been using this as an intro when I teach forces to my 8th graders for 5 years now :) glad to find your channel and see that you are still making new content! That's awesome ^_^ keep it up man.

[scoobyjimdoo]

Do people not take basic physics anymore? Unbalanced forces cause acceleration, therefore another force must be canceling the gravitational one. This is called the normal force.

[jagadishk]

Hey man just wanted to remind that you have come a long way, congrats. Can't believe this was 10 years ago.

[MrCmon]

Oh... the burn against philosophy students!

[veritasium]

@Tossphate I have another video that has Introducing Normal Force in the title

[nervz]

4 words..
a
push
or
pull

forces that acting on you atm:
-force of gravity (force on person exerted by earth)
-newtons third law tells us that you, the person, exerts a force on the earth that's equal and opposite
-theres a normal force exerted by the earth thats equal to the force of gravity b/c of newtons 2nd law stating that no a=equal forces
-windy day means air resistance, so the force of air
-again, the force on person exerted by the air means there's an equal and opposite force on air thats exerted by the person.
-static friction force also prevents you from moving, so newtons second law tells us that the force of static friction is equal to any other horizontal forces.

[MarkoDinicDinke]

The best part of interviewing people are the freaky answers. :)

[brunopbch]

Force is the measure of interaction between bodies. That's the best answer I've ever learned.

[arttom]

I think a lot of us would look as silly if an expert in a field in which we're not acquainted asked us questions

[zahraakhalife]

I have watched this video before, and I'm watching it again now. It has been since 2014 or 2015 that I started watching Veritasium, and I love it.

[iwontliveinfear]

well the gravitational force doesn't pull me down to the earth, it pulls me and the earth toward each other.
That keeps the centrifugal force of the Earth's rotation from slinging me out into space.
Inside my body, there are the atomic forces at work, the strong force keeps the nuclei of my atoms together. The electromagnetic force is responsible for keeping me together at the molecular level, as well as keeping me from passing through other objects.
The atomic weak force is responsible for radioactivity, it is believed that it is also (at least in part) responsible for the transmission of smell.
Atmospheric pressure is largely another expression of the gravitational force.
All that, and that isn't counting the elector-chemical interactions in my brain and nervous system to tell my thumb to overcome inertia and fiction by unleashing potential energy stored in my muscles into kinetic energy to Swype patterns across my pocket computer's touch interface keyboard to compose and transmit this information.

[kirangtkl]

If iam standing (without any motion)
1.gravitational force: which pulls me down
2.Normal force which opposes the body from gravitation
While motion (first 2 forces are necessary which I mentioned above and other two forces also necessary to move)
1.To move forward I need frictional force, with out frictional force you are slipping (no grip)
2. Muscular force inside you

[Clint]

Force is rate of change of momentum with respect to time:

F= d(mv)/dt

Thus via the product rule:

F = v(dm/dt) + m(dv/dt)

typically we can regard the mass of an object as constant (ignoring things such as relativity and rocketry) so dm/dt = 0

so:
F = 0 + m(dv/dt)

dv/dt is the rate of change of velocity with time, i.e. acceleration
dv/dt = a

Therefore:

F = ma

Congratulations, you just derived newtons second law of motion.
:)