A jet plane lands with velocity of 100m/s and can accelerate at a maximum rate of -5m/s2 as it come to rest. From the instant it touches the runway, what is the minimum time needed before it stops?

Ahanging spring stretches by 35.0 cm when an object of mass 450 g is hung on it at rest. in this situation, we define its position as x = 0. the object is pulled down an additional 18.0 cm and released from rest to oscillate without friction. what is its position x at a moment 84.4 s later? express your answer in cm.