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http://img15.imageshack.us/img15/858/masteringf.jpg [Broken]

a:

550-150 = 400rev change

400/60 = 6&2/3 rev/s (converted to revs)

6.66666 / 3.5 seconds = 1.9 rads^-2

since it's decelerating i put -1.9 rads^-2

now part two i got wrong,

b:

[tex]\theta[/tex]f=[tex]\theta[/tex]i + [tex]\omega[/tex]i * t + 1/2 [tex]\alpha[/tex] t^2

so i got the angle it turns through in radians being

wi * t + 1/2at^2

wi = 550*2[tex]\pi[/tex][tex]\underbrace{}_{}[/tex]t

wi = 57.59 rad/s (please check this i think this may be where i went wrong)

so radian angle = 57.59 *3.5 + (1/2*(-1.9) ) *3.5^2

i got 189 radians

189 / 2[tex]\pi[/tex] = 30 revolutions

and i got it wrong

c: part three of the question:

wf = wi + at

0 = wf (from question) + at

wf = (150 *2[tex]\pi[/tex])/60 = 15.7 rad/s

0 = 15.7 + (-1.9 *t)

-15.7/-1.9 = t

t=8.26 seconds

and i got it wrong

a:

550-150 = 400rev change

400/60 = 6&2/3 rev/s (converted to revs)

6.66666 / 3.5 seconds = 1.9 rads^-2

since it's decelerating i put -1.9 rads^-2

now part two i got wrong,

b:

[tex]\theta[/tex]f=[tex]\theta[/tex]i + [tex]\omega[/tex]i * t + 1/2 [tex]\alpha[/tex] t^2

so i got the angle it turns through in radians being

wi * t + 1/2at^2

wi = 550*2[tex]\pi[/tex][tex]\underbrace{}_{}[/tex]t

wi = 57.59 rad/s (please check this i think this may be where i went wrong)

so radian angle = 57.59 *3.5 + (1/2*(-1.9) ) *3.5^2

i got 189 radians

189 / 2[tex]\pi[/tex] = 30 revolutions

and i got it wrong

c: part three of the question:

wf = wi + at

0 = wf (from question) + at

wf = (150 *2[tex]\pi[/tex])/60 = 15.7 rad/s

0 = 15.7 + (-1.9 *t)

-15.7/-1.9 = t

t=8.26 seconds

and i got it wrong

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