[填空题]
The blades in a blende/(rgf8 u:rm7u+rk qit r rotate at a rate of 6500 rpm. When the mo -,3j4vx* 4sxrpwa nwjtor is turned off during operation, the blades slow to rx 4px ,jvw4*-w3jarsn est in 3.0 s. What is the angular acceleration as the blades slow down? $rad/s^2$