Lecture 29 - Hydrodynamics in Sports II

Question 1

how can we use drag force to our advantage?

Answer 1

• can propel us forward
• due to pressure differences
• becomes propulsive force

Question 2

how can we produce even more propulsive force?

Answer 2

• producing a lift force along with a drag force
• hand must be slightly curves to generate lift

Question 3

what is paddling?

Answer 3

• the action of gaining propulsion via drag force alone
• less efficient than using lift

Question 4

what is skulling?

Answer 4

• the action of using both drag force and lift
• knifing through the water
• harder to do and control, but more efficient

Question 5

how do you perform skulling instead of paddling?

Answer 5

• increase the sideways motion of hands by making hand path not straight
• path should be a long curve/loop

Question 6

what should the arm do after performing skulling?

Answer 6

• pull the rest of the body forward past the “fixed hand”
• like climbing a ladder

Question 7

how does the goal of the hand change with different strokes?

Answer 7

• it doesn’t
• always should create a fixed handle to pull on the water and maximize sideways pathway to maximize lift

Question 8

how is skulling used in a whip kick?

Answer 8

• skulling motion is used to produce lift with the feet
• the goal is to push off of a fixed handle to maximize the efficiency of the kick

Question 9

how is skulling used during the egg beater?

Answer 9

• same rotational scoop method as before
• this is more efficient and therefore you can tread water longer and live longer

Question 10

what is the most efficient technique for propulsion? (not done by humans)

Answer 10

• vortices
• undulating of the body or tail
• the swivelling motion can push off of the created vortices giving them acceleration

Question 11

how do humans try to mimic the vortice method?

Answer 11

• using dolphin kick during the butterfly
• it doesn’t work because we don’t have enough speed to create vortices