Question

the truck in the figure below is going around a circular track of radius 71m, banked at a 61 degree angle. A spider rests on the inside wall of the truck. The coefficient of static friction between the spider and the truck is 0.85. Find the maximum speed that the truck can have before the spider begins to slip down the wall

Answer 1

oh boy, this is a big question for open study ;)
do you have the equation for centripital force?

Answer 2

not exactly

Answer 3

is this a physics class or dynamics?

Answer 4

physics

Answer 5

k,
centripital force, Fc = m * (v^2/r)

Answer 6

since we are looking for v, we can re-write it as
v = sqrt( (Fc*r)/m )

Answer 7

meaning we need to find Fc, and m, because we have the r

Answer 8

so now we need to sum the forces in the x and y direction of our free body diagram

Answer 9

our equation looked like; sqareroot sin theta +friction cos theta / cos theta -friction sin theta

Answer 10

but with that the denominator is negative so that cant be right

Answer 11

this one is tough!

Answer 12

which one?

Answer 13

i get sqrt(9.81 [ (sin(61) + cos (61) ] *71 )

Answer 14

its quite ugly

Answer 15

do you have a free body diagram? and did you sum the forces in the x-direction?

Answer 16

that is the same question with different numbers

Answer 17

sum the forces in the x-direction = 0 = sin(61) * 0.85 * Fn + Fn*cos(61) - Fc

Answer 18

I don't know how to open that file...

Answer 19

you cant just click on it?

Answer 20

so Fc = sin(61) * 0.85 * Fn + Fn*cos(61)

I can click , but it says i need software to view it

Answer 21

and Fn = m*g so,
Fc = sin(61) * 0.85 * mg + mg*cos(61)

Answer 22

now plug Fc into the prior equataion
v = sqrt( (Fc*r)/m )
cancel out the masses and you get
sqrt(9.81 [ (sin(61) + cos (61) ] *71 )

Answer 23

I have to go to work now though, i hope that helps!

Answer 24

thank you!