A Machinist Turns on the Power to a Grinding Wheel $38 \mathrm { rad } / \mathrm { s }$

Multiple Choice

A machinist turns on the power to a grinding wheel at time t = 0 s.The wheel accelerates uniformly from rest for 10 s and reaches the operating angular speed of $38 \mathrm { rad } / \mathrm { s }$ The wheel is run at that angular speed for 30 s and then power is shut off.The wheel slows down uniformly at 2.1 rad/s² until the wheel stops.In this situation,what is the angular acceleration of the wheel between t = 0 and t = 10s?

A) 3.8 rad/ $\mathrm { s }^2$
B) 4.6 rad/ $\mathrm { s }^2$
C) 5.3 rad/ $\mathrm { s }^2$
D) 6.1 rad/ $\mathrm { s }^2$
E) 6.8 rad/ $\mathrm { s }^2$