Newton's Laws

Newton’s First Law of MotionEvery object continues in its state of rest, or of uniform velocity in a straight line, as long as no net force acts on it.

The tendency of an object to maintain its state of rest or of uniform motion in a straight line is called inertia. As a result, Newton’s first law is often called the law of inertia.

Newton’s Second Law of MotionThe acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object.

The greater the mass, the less the acceleration for the same net force. The mathematical relation, as Newton argued, is that the acceleration of an object is directly proportional to its mass.

Newton’s Third Law of MotionWhenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first.

Observations suggest that a force applied to any object is always applied by another object.

The first law applies to the state of the water.The second and third of Newton's laws apply to the raft by the fact that water is constantly in motion which applies force to the raft. The third law applies because if you hit a rock with a certain force you bounce back because of the force applied, which is then where the elasticity of the raft is needed. 

White Water Rafting Newton's Law in Action