Question

If the net unbalanced external force acting on an object is zero, then the
(A) Velocity of the object may or may not be zero
(B) Acceleration of the object must be zero
(C) Velocity of the object must be non-zero
(D) Acceleration of the object must be a non-zero constant
Choose the correct option:

• A. (A) and (B)
• B. (B) and (C)
• C. (C) and (D)
• D. (A) and (D)

Answer 1

The correct option is A (A) and (B)

According to Newton’s second law of motion, $\Sigma F=Ma$ Here, M and a are mass and acceleration of the object respectively.
Net force acting on an object, $\Sigma F=0\Rightarrow Ma=0$
$\Rightarrow a=0(\because M\ne 0)$
Therefore, the acceleration of the object is zero, if the net unbalanced external force acting on it is zero. If the object is moving, then it will keep moving with the same velocity. If the object is at rest, then it will remain at rest. Thus, the velocity of the object may or may not be zero. Therefore, the statements (A) and (B) are correct.
Hence, the correct answer is option (1).