Centripetal acceleration question

[physics_geek]

Homework Statement

Young David who slew Goliath experimented with slings before tackling the giant. He found that he could revolve a sling of length 0.800 m at the rate of 6.00 rev/s. If he increased the length to 1.100 m, he could revolve the sling only 4.00 times per second.
(a) What is the speed of the stone for each rate of rotation?
at 6.00 rev/s
at 4.00 rev/s

(b) What is the centripetal acceleration of the stone at 6.00 rev/s?


(c) What is the centripetal acceleration at 4.00 rev/s?

Homework Equations

a = v^2/r
T = 2(pi)r/v

The Attempt at a Solution

a = (6.00 rev/s)^2/.800 m = 45m/s^2





im not sure if I am even doing this rite..how do i get the speed?
do i have to convert rev/s to anythin?

 

[LowlyPion]

Homework Statement

Young David who slew Goliath experimented with slings before tackling the giant. He found that he could revolve a sling of length 0.800 m at the rate of 6.00 rev/s. If he increased the length to 1.100 m, he could revolve the sling only 4.00 times per second.
(a) What is the speed of the stone for each rate of rotation?
at 6.00 rev/s
at 4.00 rev/s

(b) What is the centripetal acceleration of the stone at 6.00 rev/s?

(c) What is the centripetal acceleration at 4.00 rev/s?

Homework Equations

a = v^2/r
T = 2(pi)r/v

The Attempt at a Solution

a = (6.00 rev/s)^2/.800 m = 45m/s^2

im not sure if I am even doing this rite..how do i get the speed?
do i have to convert rev/s to anythin?

You are on the right track but you didn't treat the 2π factor correctly.

a = v²/r

v = w * R = 2πf * R

a = (2πf* R)²/R = 4π²*f²*R

 

[physics_geek]

what do w and n stand for?

 

[LowlyPion]

what do w and n stand for?

w is angular velocity little omega

And that's not N. Let me copy it in a different font.

a = v²/r

v = w * R = 2πf * R

a = (2πf * R)²/R = 4π² * f² * R

 

[physics_geek]

cool
thanks a lot