The work required to accelerate an object initially at rest to a speed v f is W. What is the additional work needed to increase its speed from v f to 2 v f? W
W/2

2W

3W

none of them

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.