An object is attached to a vertical ideal massless spring and bobs up and down between the two extreme points A and B.When the kinetic energy of the object is a minimum,the object is located
A) at either A or B.
B) midway between A and B.
C) 1/3 of the distance from A to B.
D) 1/4 of the distance from A to B.
E) 1/ times the distance from A to B.

Question

An object is attached to a vertical ideal massless spring and bobs up and down between the two extreme points A and B.When the kinetic energy of the object is a minimum,the object is located
A) at either A or B. 
B) midway between A and B. 
C) 1/3 of the distance from A to B. 
D) 1/4 of the distance from A to B. 
E) 1/ times the distance from A to B.

Quizplus · Accepted Answer

When the object is at either A or B, it comes to a stop for a moment before moving in the opposite direction. At this instant, the velocity of the object is zero, which means that its kinetic energy is also zero. This is the only point where the kinetic energy can be minimum. At any other point in the trajectory, the object would have both kinetic and potential energy which would add up to a higher value. Therefore, the answer is choice A.

An Object Is Attached to a Vertical Ideal Massless Spring