Why Can't a Conical Pendulum's String Be Horizontal?

[Hugofung]

Such as the figure

Why the string could not be horizontal when the rubber bungis moving in a horizontal circle?
Only moving at conical pendulum?

By the way, if tension is equal to weight(W), have any conclusion?

 

[CWatters]

Why the string could not be horizontal when the rubber bungis moving in a horizontal circle?

Write an equation for the vertical forces acting on the bung. Set θ = 90 and see what happens.

 

[andrevdh]

What do you know about the force that is required to make an object move in a circle?

 

[Hugofung]

What do you know about the force that is required to make an object move in a circle?

centripetal force

 

[andrevdh]

Correct. That is the resultant force on the object needs to point to the centre of the circle.
In this case it means that the resultant of the two vectors must point to the center of
the circle. If the string could be horizontal where would the resultant lie?