_WCLN - Physics - Net Forces & Normal Force
This is the third Net force video. This one adds normal forces.
#physics #forces #netforce #phet #pull #push #normalforce #normal
0:00at this point we're getting pretty good at drawing free body diagrams and
0:04determining that forces we first worked on horizontal surface since then we
0:11learned how to do vertical situations where the objects were falling in this
0:16tutorial we're going to consider critical situations again but in this
0:20case the objects aren't falling let's consider a book on the table the book
0:27weighs five Newton's the free body diagram would include low gravity
0:33pointing down five mutants and well there must be some other force on this
0:40book as our free body diagram is the exact same as if it were falling book
0:46and what we know that the book isn't falling it's just sitting there on the
0:50table so where is this other force coming from it must be from the table if
0:58we removed the table the book which surely fall so that Tebow is opposing
1:03the force of gravity by keeping the book from falling to the ground
1:09the forests that the table is providing we call the normal force since the book
1:16is clearly balanced sitting there and not moving the forces must be balanced
1:22as well
1:24therefore we know that the normal force must be 5 Newton's up to balance so with
1:33the gravitational force 5 Newton's down there for the net force would be zero
1:41the forces are all balanced and the book continues to just sit there
1:49if you're standing on the ground the ground is providing a normal force
1:54pushing you up if you weigh 500 Newton's your free body diagram would include the
2:01gravity pulling you down and the normal force provided by the ground pushing
2:08back up and the normal force would be 500 Newton's therefore your net force
2:15would be 500 Newton's down minus 500 Newton's up or a net 470 your forces
2:25would be balanced and you'd be able to just stand there
2:32if you're
2:33scherer the chair is providing a normal force on you
2:38pushing you back up if you wait six hundred Newton's your free body diagram
2:44would include that gravity pulling you down and then normal for us in this case
2:51provided by the chair pushing back up and the chair would provide a normal
2:57force of six hundred Newton's so that your net force could be 600 Newton's
3:03down minus six hundred Newton's up 40 again your forces are balanced and
3:10you're able to sit there in the chair
3:15take a moment to look around you all those items sitting on the ground or on
3:22tables or on book shows all have a normal force keeping them from falling
3:29towards the center of the earth if you put something on a table that is too
3:35heavy
3:36that is the table isn't strong enough to provide the required normal forests to
3:41balance its own then the table will break and it'll all fall towards the
3:47ground any table or shelf that's not breaking is able to provide the normal
3:56force required to balance the forces and make after net equal to 0
4:03as we seemed normal forces in most cases simply oppose gravitational forces but
4:10you can create an exception to this let's go back to her five Newton book
4:15just sitting on the table now what if you push down on the book with an extra
4:21force of ten Newton's then the free body diagram would have an extra force we
4:28have the force of gravity and the normal force but now this extra force of ten
4:35Newton's pushing down now if the book continue to be held up by the table that
4:41is it could handle all these forces than normal force would have to balance both
4:47for the forces pushing down so we have five new teams down to force of gravity
4:52but then an extra 10 Newton's down and those we can add for a total of 15
4:59Newton's pushing down so for ethnic to be 0 the normal force in this case would
5:07now have to be fifteen Newton's pushing back up then normal force will continue
5:15to increase as needed until it reaches a force that it can't handle then the
5:21table will break and everything will fall to the ground
5:26in this tutorial we were introduced to normal forces normal forces are simply
5:34forces that hold things up
5:36normal forces are provided by the ground or tables or bookshelves or your hand or
5:43anything else that strong enough to oppose the gravitational force on an
5:47object we also looked at a case where the normal force not only had to oppose
5:53the gravitational force but also had to impose an extra force that was being
5:58added to the object