Question

# The wheel of a motor, accelerated uniformly from rest, rotates through 2.5 radian during the first second. Find the angle rotated during the next second.  10 rad  7.5 rad  5 rad 12.5 rad

Solution

## The correct option is B 7.5 rad  As the angular acceleration is constant, we have θ = ω0t + 12αt2 = 12αt2 Thus, 2.5 rad = 12 α (1s)2         α = 5 rad/s2 or      α = 5 rad/s2 The angle rotated during the first two seconds is         = 12×(5rads2)(2s)2 = 10 rad. Thus, the angle rotated during the 2nd second is 10 rad - 2.5 rad = 7.5 rad.

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