Newton's First Law
An object In motion or at rest tends to stay at rest until an unbalanced force acts upon it
When you start the match, the opponent is at rest. When you start to take him down, You pick him up and take him down. When you pick him up, you there is an unbalanced force that picks the opponent up to drive him down. When the opponent tries to take a shot, you sprawl, and push the guy down. That is an unbalanced force acting upon the opponent
Newton's Second Law
The acceleration of an object is the force divided by the mass
Let's say there is a wrestling match with the weight class at 138 pounds and 70 pounds. At the 138 pound class, they weigh heavier, and at the 70 pound class, they weigh less. Since Newton's second law says the acceleration depends on how much force and mass is in an object, when you take down a guy weighing 138 pounds, you will need a lot more force than a guy weighing 70 pounds. When you apply the same amount of force to both people, the guy weighing 70 pounds will move a lot farther than the guy weighing 138 pounds, because of the mass of the two men.
Newton's third law
For every action, there is an opposite, equal reaction.
When you are in referee's position, you have to get off the ground. When you start to push yourself off the ground, you are technically trying to push the ground down. You can possible do that though. So when you push the ground, your body will go up. This is because of Newton's third law of motion.