Car curves at a radius of 50m while travelling at 100km/hr

[MissJewels]

Homework Statement

Calculate the centripetal acceleration module in the following cases as a multiple of g = 9.8 m / s ^ 2.
a) a car traveling at 100km / h on a curve of radius 50m.
b) a jet plane flying at 1,500 km / h and making a turning radius of 5km.
c) a stone that is rotated every 0.5 s after a string of length 1 m
d) a speck of dust on the edge of a disk of 30 cm diameter rotating at 33.33333 ... rev / min.
e) a molecule in a centrifugal radius of 15cm rotating at 30,000 rev / min.

Homework Equations

a)

g= 9.8 m/s²
a_r = v²/r
a_r = ug

u: coefficient of friction(WHERE DO I GET THIS?!)

haven't touched b) and on yet..

The Attempt at a Solution

so here's how i began...
converted:
v_i = 100km/h = 10 000m/3600s = 27,78m/s
a_r= 100²/50 = 200 m/s²

a_r = 9,8u

Okay... so how do i get the coefficient of friction(u) if I am not given any mass value?

 

[RTW69]

You don't need the coefficient of Friction for these problems. Convert the velocity to m/s. Square it and divide by the radius in meters to get a_c. Divide by 9.8 to get the multiple.

You will need to find the angular velocity for some of these problems and be able to convert from revolutions/min to radians/sec

 

[MissJewels]

You don't need the coefficient of Friction for these problems. Convert the velocity to m/s. Square it and divide by the radius in meters to get a_c. Divide by 9.8 to get the multiple.

You will need to find the angular velocity for some of these problems and be able to convert from revolutions/min to radians/sec

That's awesome, thanks! I got a, b, and c, but I am stuck on d ... given its diameter, where do i go from there?

 

[RTW69]

Remember that a_c=r*ω² you have r you need to find ω, the angular velocity. The units are radians/sec. The stone makes 1 revolution in .5 seconds. 1 revolution is how many radians? Divide that number by 0.5 sec

 

[MissJewels]

Remember that a_c=r*ω² you have r you need to find ω, the angular velocity. The units are radians/sec. The stone makes 1 revolution in .5 seconds. 1 revolution is how many radians? Divide that number by 0.5 sec

I got it, thanks!

 

[MissJewels]

You don't need the coefficient of Friction for these problems. Convert the velocity to m/s. Square it and divide by the radius in meters to get a_c. Divide by 9.8 to get the multiple.

You will need to find the angular velocity for some of these problems and be able to convert from revolutions/min to radians/sec

I'm doing the d right now...
found that r= 0,015m
w = 0,349 rad/s
and used the equation:
ac=r*ω2
and got ac= 0,0018

then divided it by 9,8... and got 1,84 x10^-4g... when the right answer should just be 1,87g
HELP?

 

[RTW69]

radius is not .015m
ω is not .349 rad/s
Recheck these values and recalculate