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 reaches its highest point, all of its potential energy is converted into kinetic energy. As the object falls towards its lowest point, its kinetic energy increases and potential energy decreases. At the lowest point, all of its potential energy is converted back into kinetic energy, and so the object has the maximum kinetic energy. 
Therefore, at the minimum kinetic energy point, the object must be at either A or B, where the velocity is zero and hence the kinetic energy is minimum.

An Object Is Attached to a Vertical Ideal Massless Spring