A Machinist Turns on the Power on to a Grinding $96 \mathrm { rad } / \mathrm { s } .$

question 116

Multiple Choice

A machinist turns on the power on 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 $96 \mathrm { rad } / \mathrm { s } .$ The wheel is run at that angular velocity for 40 s and then power is shut off.The wheel slows down uniformly at $1.5 \mathrm { rad } / \mathrm { s } ^ { 2 }$ until the wheel stops.For how long a time after the power is shut off does it take the wheel to stop?

• A)64 s
• B)62 s
• C)66 s
• D)68 s
• E)70 s