Speed and accleration of a turntable

[clope023]

Homework Statement

An electric turntable 0.740m in diameter is rotating about a fixed axis with an initial angular velocity of 0.290rad/s . The angular acceleration is 0.900rad/s^2 .

a) Compute the angular velocity after a time of 0.194s. - .465rev/s

b) Through how many revolutions has the blade turned in this time interval? - .073rev

c) What is the tangential speed of a point on the tip of the blade at time t = 0.194s ?

d) What is the magnitude of the resultant acceleration of a point on the tip of the blade at time = 0.194 ?

Homework Equations

v = r$$\omega$$

arad = $$\omega$$^2r

atan = r$$\alpha$$

The Attempt at a Solution

for part c)

v = (.740/2)(.465) = .172m/s wrong

for part d)

arad = (.465)^2(.740/2) = .0800m/s^2

atan = (.740/2)(.900) = .333m/s^2

a = (.0800^2 + .333^2)^(1/2) = .342m/s^2 wrong

I'm not sure what I'm doing wrong, any help is appreciated.

 

[bgask001]

For part C it seems as if you need to do is convert the revs to meters. To do this you need to know the circumference (which would be the distance "unrolled" after 1 revolution)