ATC Aquatic Kinesiology & Biomechanics 1 — Questions and Answers
Question 1: According to Archimedes' principle, the buoyant force acting on an immersed object is equal to:
- The weight of the object
- The weight of the water displaced by the object (Correct answer)
- The volume of water surrounding the object
- The density of the water multiplied by gravity
Correct answer: The weight of the water displaced by the object
Archimedes' principle states that the buoyant force equals the weight of the fluid displaced by the object, not its own weight.
Question 2: Which characteristic of water creates resistance to movement that increases with the square of the patient's velocity?
- Buoyancy
- Hydrostatic pressure
- Drag force (Correct answer)
- Surface tension
Correct answer: Drag force
Drag force is proportional to velocity squared (F ∝ v²), so doubling speed quadruples resistance, making velocity the most powerful progression variable in aquatic therapy.
Question 3: In the human body, the center of buoyancy is typically located in which region?
- Pelvis
- Lower lumbar spine
- Upper chest and thorax (Correct answer)
- Umbilical region
Correct answer: Upper chest and thorax
The center of buoyancy resides in the upper chest because the air-filled lungs make this region less dense, positioning it superior to the center of gravity.
Question 4: The average specific gravity of the human body is approximately 0.97. What is the primary clinical implication of this value?
- Most patients will sink unless supported by equipment
- Most patients can float because their density is slightly less than water (Correct answer)
- Patients require weights to remain submerged for deep-water exercise
- Buoyancy forces will compress rather than unload joints
Correct answer: Most patients can float because their density is slightly less than water
A specific gravity below 1.0 (water) means the body is less dense than water, allowing most individuals to float with minimal effort.
Question 5: According to Pascal's law, hydrostatic pressure in aquatic therapy increases proportionally with:
- Water temperature
- Depth of immersion (Correct answer)
- Patient body surface area
- Water salinity alone
Correct answer: Depth of immersion
Hydrostatic pressure increases linearly with depth because the weight of the water column above a point grows as immersion deepens.
Question 6: An object will float in water when its specific gravity is:
- Equal to 1.0
- Greater than 1.0
- Less than 1.0 (Correct answer)
- Greater than 1.5
Correct answer: Less than 1.0
Objects with specific gravity less than 1.0 are less dense than water and therefore experience a net upward buoyant force, causing them to float.
Question 7: The viscosity of water provides therapeutic benefit in aquatic resistance exercise primarily by:
- Reducing joint compression forces
- Creating consistent resistance throughout the full range of motion in all directions (Correct answer)
- Increasing buoyancy forces on the limb
- Lowering water temperature during exercise
Correct answer: Creating consistent resistance throughout the full range of motion in all directions
Water's viscosity provides multidirectional, consistent resistance throughout the entire range of motion, enabling strengthening without the unidirectional limitation of gravity-based resistance.
ATC Aquatic Kinesiology & Biomechanics 1
According to Archimedes' principle, the buoyant force acting on an immersed object is equal to: