A Machinist Turns on the Power to a Grinding Wheel $2.1 \mathrm { rad } / \mathrm { s } ^ { 2 }$

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 rad/s . The wheel is run
at that angular speed for 30 s and then power is shut off. The wheel slows down uniformly at
$2.1 \mathrm { rad } / \mathrm { s } ^ { 2 }$
between t=0 s and t=10 s ?

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