Which one of the following statements is not correct?
[amp_mcq option1=”If the velocity and acceleration have opposite sign, the object is slowing down” option2=”If the velocity is zero at an instant, the acceleration should also be zero at that instant” option3=”If the velocity is zero for a time interval; the acceleration is zero at any instant within the time interval” option4=”If the position and velocity have opposite sign, the object is moving towards the origin” correct=”option2″]
This question was previously asked in
UPSC NDA-2 – 2015
Statement B is not correct. If the velocity of an object is zero at a particular instant, its acceleration at that instant does not necessarily have to be zero. A classic example is an object thrown vertically upwards: at the peak of its trajectory, its instantaneous velocity is zero, but the acceleration due to gravity is still acting on it and is non-zero (approximately 9.8 m/s² downwards).
Acceleration is the rate of change of velocity. Zero velocity at an instant only means the object is momentarily stopped; it does not imply that the velocity is not changing at that instant.