At t =0 the current to a dc electric motor is reversed, resulting in an angular

Question

At t=0 the current to a dc electric motor is reversed, resulting in an angular displacement of the motor shaft given by ?(t)=( 260rad/s )t?( 19.4rad/s2 )t2?( 1.50rad/s3 )t3.

Part A

At what time is the angular velocity of the motor shaft zero?

Part B

Calculate the angular acceleration at the instant that the motor shaft has zero angular velocity.

Part C

How many revolutions does the motor shaft turn through between the time when the current is reversed and the instant when the angular velocity is zero?

Part D

How fast was the motor shaft rotating at t=0, when the current was reversed?

Part E

Calculate the average angular velocity for the time period from t=0 to the time calculated in part A.

Explanation / Answer

A)
? = d?/dt = 260 - 38.8 t - 4.5t

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