Question

The angle a rotating shaft turns through in t seconds which is given by..

Answer 1

\[\theta=\omega t+\frac{ 1 }{ 2 }\alpha t ^{2}\]
Determine the time taken to complete 4 radians if \[\omega \] is 3.0 rad/s and \[\alpha \] is 0.60 rad/s^2

Answer 2

so isnt it just
4 = 3t + 1/2 *.6*t^2...?

Answer 3

so solve for t using quadratic solution after putting in the form of
0 = ax^2 + bx + c

Answer 4

answers are t = -11.19 and
t = 1.19
so it will turn 4 radians 11 seconds before you turn it on
...
OR
it will turn 4 radians 1.2 seconds after you turn it on

take your pick @WilliamF

Answer 5

How did you rearrange it into a quadratic?

Answer 6

sorry dude, was looking at another post, back now

Answer 7

no worries

Answer 8

you already had the form there
theta = bx + (a) x^2
so theta is -c
rearrange so it equals 0
0 = ax ^2 + bx + c
you get your c as -4
your b as 3 (angular velocity)
and your a as .5*.6 = 0.3 (half angular acceleration)

... done ;)

Answer 9

and in this example x = time = t

Answer 10

ok I get it now, thanks for the help Jack

Answer 11

always welcome dude