Yes, a moving particle can be pushed backwards by another force. When a particle experiences a force in the opposite direction to its motion, its velocity and momentum can change accordingly.
If a particle is initially moving forward with a certain velocity and is pushed backward by an external force, its velocity will decrease. The direction of the velocity will also change to align with the direction of the force. The particle's momentum, which is the product of its mass and velocity, will also decrease since both mass and velocity are changing.
In terms of the conservation of momentum, if the particle is pushed backward, the force exerted on it will cause a decrease in its momentum. This change in momentum must be balanced by an equal and opposite change in momentum of the object exerting the force. According to Newton's third law of motion, the force exerted by the particle on the other object is equal in magnitude but opposite in direction to the force exerted by the other object on the particle.
In summary, when a moving particle is pushed backward by another force, its velocity and momentum decrease, and the direction of its velocity changes to align with the force. The change in momentum of the particle is balanced by an equal and opposite change in momentum of the object exerting the force.