The elevator starts to move in a straight line with a square acceleration of 2m / s from standstill, changes to a uniform motion after 3S, changes to a uniform deceleration motion after 7S, and stops after 2S 1. How fast is the elevator moving at a constant speed? 2. What is the acceleration during deceleration? 3. What is the average speed of acceleration and deceleration? Complete the formula

The elevator starts to move in a straight line with a square acceleration of 2m / s from standstill, changes to a uniform motion after 3S, changes to a uniform deceleration motion after 7S, and stops after 2S 1. How fast is the elevator moving at a constant speed? 2. What is the acceleration during deceleration? 3. What is the average speed of acceleration and deceleration? Complete the formula

According to the velocity formula of uniform acceleration linear motion, if the initial velocity is 0, then v = at = 2 * 3 = 6m / S2. If the uniform deceleration motion stops for 2S, then a = (vt-v0) / T = (0-6) / 2 = - 3m / S23. The average velocity of uniform acceleration linear motion can be expressed as half of the sum of initial velocity and final velocity, then the average velocity of acceleration phase V1 = (0 + 6) / 2 = 3m / s