The correct answer is kg m s^(–1). Explanation & Key Takeaways: • Momentum is a fundamental concept in physics, defined as the quantity of motion an object possesses. It is mathematically expressed as the product of an object's mass and its velocity (p = m × v). • To determine the SI unit of momentum, we analyze the basic units of the physical quantities involved. The SI unit for mass is the kilogram (kg), and the SI unit for velocity is meters per second (m/s or m s^(–1)). • By multiplying these base units (kg and m s^(–1)), we derive the SI unit for momentum as kg m s^(–1). Hence, option D is correct. • Momentum is a vector quantity, meaning it possesses both magnitude and direction. The direction of the momentum vector is always the same as the direction of the velocity of the object. • The unit kg m s^(–2) represents the Newton (N), which is the SI unit of Force, not momentum. Hence, statement/option B is incorrect. • The unit g m s^(–1) is a metric unit but not the standard International System of Units (SI) unit, as the SI system requires mass to be in kilograms. Hence, statement/option A is incorrect. Related Concepts: • Newton's Second Law of Motion: This law states that the force applied to an object is equal to the rate of change of its momentum (F = dp/dt). This establishes a direct relationship between force, mass, and acceleration. • Law of Conservation of Momentum: In the absence of an external force, the total momentum of a closed system remains constant. This principle is vital in analyzing collisions and explosions, where the initial momentum equals the final momentum. • Impulse: Impulse is defined as the change in momentum of an object when a force acts upon it for an interval of time. The SI unit for impulse is the Newton-second (N s), which is dimensionally equivalent to kg m s^(–1). • Factors Affecting Momentum: • Mass: If two objects travel at the same velocity, the one with the higher mass will have greater momentum. For example, a truck has more momentum than a bicycle moving at the same speed. • Velocity: If two objects have the same mass, the one with the higher velocity will have more momentum. A bullet, despite its small mass, has immense momentum due to its extremely high velocity. • Applications: The concept of momentum is used in designing safety features in vehicles, such as airbags and crumple zones, which aim to increase the time over which the momentum changes during a crash, thereby reducing the impact force. Important Notes: • The CGS unit of momentum is g cm s^(–1) (gram-centimeter per second). • In Relativistic Mechanics, the formula for momentum changes as the velocity approaches the speed of light (c), incorporating the Lorentz factor. • The dimensions of momentum are [M L T^(–1)]. • An object at rest has a velocity of zero, and therefore its momentum is also zero, regardless of its mass.