Water Safety Instructor (WSI) Practice Exam

What does the law of acceleration state?

1. Direction and speed are independent

2. Change in speed depends on the force applied

3. Everything moves at a constant speed

4. Water resistance greatly affects acceleration

The correct answer is: Change in speed depends on the force applied

The law of acceleration, as defined by Newton's second law of motion, states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This means that the change in speed—acceleration—of an object depends on the amount of force applied to it. When a greater force is applied, the object experiences a greater acceleration, leading to a larger change in speed. In the context of water safety, understanding this principle is essential for instructors when teaching skills related to swimming and movement in the water. For instance, when a swimmer applies more force in their strokes, they will accelerate faster through the water. Knowledge of this principle allows instructors to effectively teach techniques that optimize a swimmer's movement and speed in water. The other statements do not accurately describe the law of acceleration. For instance, saying that direction and speed are independent lacks the necessary relationship between force and acceleration. A statement claiming that everything moves at a constant speed ignores the dynamics of motion that the law of acceleration addresses. Lastly, while water resistance does play a role in the movement of objects through water, it does not encompass the fundamental principle set by the law of acceleration itself.