18. Momentum is (A) the push or pull that forces an object to change its speed or direction (B) the rate of change of velocity (C) the rate at which an object changes position (D) the tendency of an object to continue moving in the same direction

The correct answer is (D) the tendency of an object to continue moving in the same direction.<br /><br />Momentum is a physical quantity that represents the quantity of motion of an object. It is defined as the product of the mass of an object and its velocity. Momentum is a vector quantity, meaning it has both magnitude and direction.<br /><br />Option (A) is incorrect because it describes force, not momentum. Force is the push or pull that causes an object to change its speed or direction.<br /><br />Option (B) is incorrect because it describes acceleration, not momentum. Acceleration is the rate of change of velocity.<br /><br />Option (C) is incorrect because it describes velocity, not momentum. Velocity is the rate at which an object changes position.<br /><br />Option (D) is correct because it accurately describes momentum. Momentum is the tendency of an object to continue moving in the same direction, and it is conserved in closed systems where no external forces are acting.