Help with a angular velocity question

[someboy]

hi i am a beginner at physics. my teacher just gave me this problem for a make up work but he did not give me any equations on solving this problem due to some misunderstanding he got mad at me. so here i am stuck... please help!


A discus thrower (arm length 1.2 m) starts from rest and begins to rotate
counterclockwise with a constant angular acceleration of size 2.7 rad/s2.
a. How long does it take for the discus thrower's angular speed to reach 5.7
rad/s?
b. How many revolutions does it take for the discus thrower's angular speed to
reach 5.7 rad/s?
c. What is the linear speed of the discus at 5.7 rad/s?
d. What is the linear acceleration of the discus at this point?
e.What is the size of the discus's centripetal acceleration?
f. What is the size of the discus's total acceleration?



i searched all over the internet and i still can't find any equations that applys to my questions here is the only question i found.. i don't even know how to use this equation on solving those problems..

O=O(initial)+ W(intial)T + 1/2 XT(square)

please begging on my knees for some help on solving this problem!

any helps would be appreciated!

 

[physixguru]

here the arm length becomes the radius of rotation..

initial angular velocity=0
alpha[accln]=2.7 rad/s^2
final angular velocity=5.7rad/s
>>5.7=0+2.7 *t

calculate t...

for next part=1 revolution=2 pi rad..

for next part..
linear velocity= angular velocity*radius

for next part..
linear acceleration=linear velocity/time

for next part..
centripetal accln=linear velocity^2/radius

total accln=[centripetal acceleration^2+tangential accln^]^1/2

tangential accln=linear accln=v/t

 

[physixguru]

are you now able to solve it?

 

[someboy]

well is there also a equation for linear velocity and angular velocity?

because i need to show work i am trying to write out the equation in letters from the helps you provided.

thank you very much!

 

[someboy]

i need a little more help how do i get the linear velocity and angular velocity is?

 

[Go Angels]

I'm having trouble on a similar problem, involving tangetial acceleration and radial acceleration; which I guess equates to linear and angular. Sorry I can't help you.

Btw, what is the name of your textbook?

 

[someboy]

it is call the physics of everyday phenomena ... it is basically uselesss it doesn't give the equation at all... only explains stuff

 

[Go Angels]

Hmmm, my textbook doesn't have anything about "angular velocity." But I think linear velocity is just the normal velocity equation of v = x/t. Don't take my word for it though. I'm horrible at physics.

 

[someboy]

yeah i am very horrible at physics but i waited for 1 hour infront of my couselor's officer and she won't even let me drop one class >_<. i still got finals tomorrow ! i guess.. i will go now... hope you can somehow solve your problems too GO angels...

really appreciate your help physixguru! you are my live saver!

 

[Go Angels]

Wow finals. Best of luck to you!

 

[physixguru]

angular velocity= linear velocity/ radius

angular velocity=angular acceleration*time

linear velocity=angular velocity* radius of rotation

linear velocity=linear acceleration*time