Final answer:
Option 1, kg m/s, represents the correct unit for momentum, as it signifies mass times velocity, aligning with the definition of momentum in physics.
Step-by-step explanation:
The valid unit for momentum among the options given is kg m/s. Momentum is defined as the product of an object's mass and its velocity, which means its unit is mass (kg) times velocity (m/s). This aligns with the principle of conservation of momentum commonly dealt with in Physics.
Option 1, kg m/s, is the correct unit for momentum, as it directly reflects the mass times velocity definition. Option 2, m/s², refers to acceleration. Option 3, Newtons (N), signifies force and is equivalent to kg m/s², as per Newton's Second Law. Option 4, Joules (J), denotes energy and is equivalent to kg · m²/s².
For instance, if an object has a mass of 2 kg and is moving at a velocity of 3 m/s, its momentum would be 6 kg m/s. This unit describes how much 'motion' the object has and is used to predict the results of collisions and interactions in dynamics.