I need to know how much force is required in order to stop a skateboard.?

Question

The combined weight of skateboard and user is 80kilos
The brake pad acts on two wheels which are 30mm x 60mm each.
The board is travelling at a speed on 20mph.
"how much force is required in order to stop the board, and what would the total stopping distance be?
There must be some kind of eqation(s)

The combined weight of skateboard and user is 80kilos
The brake pad acts on two wheels which are 30mm x 60mm each.
The board is travelling at a speed on 20mph.
"how much force is required in order to stop the board, and what would the total stopping distance be?
There must be some kind of eqation(s) The friction coefficient is normally 0.8

the stopping distance need to be 10 meters!

Man...can i have sensible answers please!
stones, walls etc arn't good answers.

Answer 1

A wall should do it.

Answer 2

The required force depend on the time it takes to stop the skateboard . you know the skateboard do not stop instantly and whatever be the origin of the force, it takes some times to stop it.
the greater the force, Time will be lesser. for example if it hit a wall(Impact) the force is great and time is small. and if you want to stop it by frictional force(which is small) the time will be long.

E=F * x where
F=applied force
x=stopping distance
so
F=E/x

on the other hand, E=mV^2 then
F=mV^2/x (1)

now we must obtain x:

if the force and acceleration(during stopping) are constant we have:
x= (mean velocity) * t
x=(0+V)/2 * t
x=vt/2 where
t=stopping time
V=initial velocity of skateboard

putting x in Eq.1 we obtain:
F=mV^2/x=mV^2/(vt/2)

F=2mV/t where
m=total mass of skateboard and user
V=Velocity
t=Stopping time

and in your question:
F=2*80*20/t =3200/t
( if your velocity is 20 m/s because 20mph is too slow and if it is 20km/h you should convert it to m/s by dividing 3.6)

Now you put extra detail and we can solve it in a deffrent way:
F=(The friction coefficient )*mg
F=0.8*80*9.8=627.2 N

a=F/m =(The friction coefficient )* g=0.8*9.8 =7.84 m/s^2
V^2=2ax
x=V^2/(2a)=V^2/15.68
x=vt/2 then t=2x/v
t=2*V/15.68=V/7.84

Put V in above equations and obtain t and x

Answer 3

F=ma
m=mass
a=acceleration

In this case, a is negative because your decelerating to 0. You'll end up with a negative force because it is applied in the opposite direction.

Convert the units kilos and mph to what you need and multiply.

You don't need a friction coefficient. You're fooling yourself into thinking the problem is more complicated than it really is.

Answer 4

force = mass x accelleration

in this case you are decelerating from 20 to zero so A would be 20 (even though the accelleration is negative, you cannot have a negative force) next times it by the mass of 80 kg, and you have 1600 newtons of force acting on that skateboard to stop it

Answer 5

I don't quite know how I would answer this question at the moment as I don't have the equations memorized, but to give at least one pointer, the acceleration is not -20 mph, you cant find teh acceleration without time (and having eitehr a time or acceleration woudl make this problem a whole lot easier)

Answer 6

impulse= momentum .... that is
Force x time applied = mass x velocity

v=20 mph
m= 80kg
first convert v to m/s to have consistent units.
To solve you need to know the time over which the force is applie to stop. little force takes longer time, a lot force a short time.

Answer 7

The same force that the skateboard is exerting.

Answer 8

a small stone hit just right could stop a skate board

Answer 9

I need the friction coefficient .

Answer 10

veryy easy an imovable object will stop u fasrt

Answer 11

skateboards dont come with brakes