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Units And Measurement

Question
CBSEENPH11020768

A Wheel has an angular acceleration of 3.0 rad/s2 and an initial angular speed of 2.00 rad/s. In a time of 2s it has rotated thorough an angle (in radian) of:

  • 6

  • 10

  • 12

  • 4

Solution

B.

10

Angular acceleration is time derivative of angular speed and angular speed is time derivative of angular displacement.
By definition,
straight alpha space equals space dω over dt
ie comma space dω space equals space αdt
So comma space if space in space time space straight t space the space angular space speed space of space straight a space body space changes space from space straight omega subscript straight o space to space straight omega
integral subscript straight omega subscript straight o end subscript superscript straight omega space dω space equals space integral subscript 0 superscript straight r space straight alpha space dt
If space straight alpha space is space constant
straight omega space minus straight omega subscript straight o space equals space αt
straight omega space equals space straight omega subscript straight o space plus αt
Now comma space as space by space definition
straight omega space equals space dθ over dt
Eq space left parenthesis straight i right parenthesis space becomes
dθ over dt space equals space space straight omega subscript straight o space plus αt
dθ space equals space left parenthesis straight omega subscript straight o space plus αt right parenthesis dt
So space straight m space if space in space time space straight t space angular space displacement space is space straight theta
integral subscript 0 superscript straight theta dθ space equals space integral subscript 0 superscript straight t space left parenthesis straight omega subscript straight o space plus αt right parenthesis space dt
Given comma space straight alpha space equals space 3.0 space rad divided by straight s squared comma space space equals space 2.0 space rad divided by straight s comma space straight t space equals space 2 straight s
Hence comma space straight theta space equals space 2 space straight x space 2 space plus space 1 half space straight x space 3 space left parenthesis 2 right parenthesis squared
or space straight theta space equals space 4 plus 6 space equals space 10 space rad