Answer: 7.095 rev
Explanation: since the motion of the washer is of a constant angular acceleration, then Newton's laws of motion applies.
Recall that
ω = ω0 + αt
Where α = angular acceleration = ?
ω = final angular velocity = 6.7rev/s
ω0 = initial angular velocity = 0 rev/s
t = time taken =8.8s
Since the motion of the dryer starts from rest, ω0 = 0, we have that
ω = αt
6.7 = α(8.8)
α = 6.7/8.8
α = 0.76 rev/s²
This value α = 0.76 rev/s² is a constant value and it is the same all through the motion.
When the lid of the washer was lifted, the motion was of a constant deceleration.
Recall that
θ = ω0t + αt²/2
Where θ = angular displacement
Since the washer is now decelerating, the final velocity (ω= 6.7 rev/s) of the accelerating motion now because the initial velocity of the decelerating motion.
Hence ω0 = 6.7 rev/s, α = - 0.76 rev/s² ( negative sign to denote deceleration) and t = 16.5s
By slotting in the parameters into the formulae, we have that
θ = 6.7 (16.5) + (-0.76)(16.5)²/2
θ = 110.55 - 103.455
θ = 7.095 rev
