The motor of a weed trimmer spins at 9,000 rpm.
Of the following, which factor does NOT affect the amount of time required for the motor to reach this speed?

A. The mass of the spool containing the trimmer line does not affect it.
B. The direction in which the torque is applied does not affect it.
C. The distribution of trimmer line inside the spool does not affect it.

The time it takes the motor to reach the final speed is dependent on the acceleration of the spool. From Newton's second law of motion, the net torque (τ) on the spool is equal to its moment of inertia (I) times the angular acceleration (α). The moment of inertia is dependent on the magnitude and distribution of the mass. Therefore, the mass of the spool and the distribution of the trimmer line will both affect the time it takes to reach the final speed. The direction of the torque, however, will not affect it.