Question

A boy is whirling a stone tied with a string in a horizontal circular path. If the string breaks, the stone

• A. Will continue to move in the circular path
• B. Will move along a straight line towards the centre of the circular path
• C. Will move along a straight line tangential to the circular path
• D. Will move along a straight line perpendicular to the circular path away from the boy

Answer 1

The correct option is C

Will move along a straight line tangential to the circular path

Explanation for the correct option

Option (C)

1. When the boy is whirling a stone tied with a string in a horizontal circular path, a centripetal force will act towards the center of the circular path.
2. In every moment of the circular path, the direction of motion (velocity) is directed along the tangent of the circular path.
3. When the string breaks, then the centripetal force will vanish. According to Newton's law, the body will move along the tangential path, because it wants to continue its motion - due to dynamic inertia.

Diagram

Explanation for the incorrect options

Option (A)

1. When the string breaks, the centripetal force will vanish. There will be no force acting towards the center of the circular path.
2. So, after breaking the string, the stone will not rotate in the circular path.,

Option (B)

1. When the string breaks, the centripetal force will vanish. That's why the stone will move tangentially.
2. So, it is not possible for the stone to move move along a straight line towards the centre of the circular path

Option (D)

1. When the string breaks, the centripetal force will vanish. That's why the stone will move tangentially.
2. So, it is not possible for the stone to move along a straight line perpendicular to the circular path away from the boy.

So, option (C) is correct.