Understanding Normal Force in High-Speed Vehicles

good morning today we are going to investigate situations where the normal force is not

equal to the weight or the force of gravity so for cars that travel at very high speeds

performance cars or sports cars often they generate a force called a downforce and that downforce

literally pushes the car into the ground now it turns out that downforce helps

cars negotiate turns at a higher speed so let's examine the forces acting on this car

when down force is involved so of course the car always has gravity acting on it

or weight 8 000 newtons and of course there is a support force or a normal force

it's the ground pushing back up on the car and so the question is how large

is the normal force when we have a down force of 15 000 newtons and a force of gravity or a weight of

8000 newtons how big is this vector well important to know is that the car

is not moving up or down if we didn't know that then we couldn't figure out this problem so we'll assume

the car is not moving up or down and that means the acceleration is zero now when the acceleration is zero the

forces are balanced so i really want you to think about this acceleration is zero

that means net force has to equal zero means all the forces ultimately have to balance each other out somehow

so please pause the video your goal is to try to figure out this vector this normal force pointing

upwards how big is it okay i hope you tried this question it's 23 000. why is it 23 000

well the car is not moving up or down it's not accelerating up or down it's acceleration is zero in the up down

direction so that's the case then all the forces pushing down

have to equal all the forces pushing back up so if fifteen thousand eight thousand

twenty three thousand newtons pushes down then twenty three thousand newtons has

to push back up the normal force in this situation is 23 000 newtons down force

plus gravity equals normal force downforce plus gravity equals normal force

in this unique situation and other situations for a plane taking off

once again while it's taking off and on the runway still in contact with the runway it's not moving

up or down and so this time we have of course as always the force of gravity acting

downwards the weight of the plane acting downwards lift is what's going to ultimately get

this plane off the ground that acts upwards and there are many videos that you can watch on lift

and normal force of course is the force of the ground supporting the plane that also acts upwards

so here is our vector diagram our free body diagram well let's give some numbers here let's

say the force of gravity is 220 000 newtons let's say the lift force currently is

190 000 newtons and the question is how big is a normal force key remember though is that it hasn't

taken off yet so it's acceleration and the up down direction is zero

please pause the video now okay i hope you've given this some thought

again the net force is zero somehow all these forces acting together let's create a situation where

everything is balanced and so this time our equation would be all the forces acting down in this case

gravity have to equal all the forces acting upwards

gravity is equal to normal plus lift and so the normal force would be 30 thousand

thirty thousand plus a hundred and ninety thousand is equal to two hundred and twenty

thousand newtons all the forces acting up have to equal all the forces acting down

in this situation because the forces are balanced there's one more video that clearly

shows this for a plane that's actually taking off a simulation video

you may want to watch that have a great day