SSC Selection Post 2025 PYQ — Question 8

Correct Answer: The stone experiences a constant acceleration directed towards the centre of the circle

Explanation

When an object moves in a circular path at a constant speed, its velocity is constantly changing because velocity is a vector quantity that depends on both speed and direction. Since the direction of motion changes at every point along the circular path, the object is undergoing acceleration, even though its speed remains constant. This acceleration is known as centripetal acceleration, and it is always directed toward the center of the circle.

Key Points

• Although the speed (magnitude of velocity) is constant, the velocity vector is constantly changing direction.
• The acceleration responsible for this change in direction is called centripetal acceleration.
• Centripetal acceleration is always directed perpendicular to the velocity, pointing directly toward the center of the circular path.
• Since there is a non-zero acceleration, the motion is considered accelerated motion, even if the speed is uniform.

Additional Facts

• If the speed of the object were also changing, the object would experience both centripetal acceleration and tangential acceleration.
• The force that provides this centripetal acceleration is called the centripetal force.
• For a stone tied to a string and whirled in a circle, the tension in the string provides the necessary centripetal force.

Important Questions

Question: What is the formula for centripetal acceleration?

Answer: It is given by a =v2/r , where v is the constant speed and r is the radius of the circular path.

Question: What happens if the centripetal force suddenly stops acting on the stone?

Answer: The stone would fly off in a straight line tangent to the circular path at the point where the force ceased, as per Newton's first law of motion.