[填空题]
The blades in a blendek*) p8;oe ;vrnt zpzhk*,-tibr rotatehye,*zu)n /zw3 t ;hfh at a rate of 6500 rpm. When the motor is turned off during operation, t eh3 f)uzh;whzy,t*n /he blades slow to rest in 3.0 s. What is the angular acceleration as the blades slow down? $rad/s^2$