biomechanics final: work, energy, power & fluid dynamics

What increases the buoyant force?

The greater the volume, the greater the density

What decreases buoyant force?

The lower the volume, the lower the density

When scuba diving, what happens when the scuba diver inhales?

The volume increases, floats

What happens when the scuba diver exhales?

Volume decreases, sink

What force always pushes the object upward?

Buoyant Force

Define wake

Turbulent flow behind the object, low pressure

What is laminar flow?

SMOOTH and regular flow of fluid particles, High pressure

How is pressure drag produced?

Difference in pressure between the front back sides of the object

What decreases relative velocity?

Tailwind

What occurs when the wake becomes larger?

Increase the pressure drag (goes slower)

Golf Club Picture: What is the benefit of the golf club?

To DECREASE the wake behind the club

What increases drag force acting on a object?

Higher air viscosity

Which of the following decreases the drag force?

Lower air viscosity

Bike Picture: Cyclist A &B, What is happening?

The drag force acting on both cyclists is reduced

Recumbent Bike Picture: Why is it more aerodynamic compared to regular commuter bike?

It has a smaller projected frontal area

How is lift force created?

By the bend/turned of the object

Ski jumper, What would reduce the drag force except?

Moving arms away from the body

Soccer ball, Magnus effect

B will go faster than side A

Right handed golfer, OPEN face, Is it going to go left or right?

It hooks to the right

Dynamic Fluid Force

Acts on a object moving within the fluid

Lift Force

By the spin/bend of the object

What does not affect buoyant force?

Mass

Tennis ball and field hockey ball, What will happen to the two balls when they are thrown, which will create dynamic fluid force?

Tennis ball because it is lighter

What happens when the laminar flow breaks off from the object earlier?

The wake increases, pressure drag increases

All of the following causes lift force except?

Acts along the line of fluid

What describes drag force except?

Directed perpendicular (it’s parallel)

What does a headwind do the relative velocity?

Increase relative velocity, go slower

What does a tailwind do to the relative velocity?

Decrease relative velocity, go faster

Which of the following increases the drag force?

Greater projected frontal area

Cars with a lower coefficient of drag?

Has good gas mileage

When looking at a power curve during a squat, what is being described by the part of the curve that is in the negative part of the graph?

ABSORB

What are the characteristics of mechanical work?

Work = Force x Displacement, Something you do, It can positive, negative, zero, Work is a way of transferring energy

Concentric contraction results in

Positive work

Isometric contraction results in

Zero work

Eccentric contraction results in

Negative work

What are examples of actions/activities that require negative work?

Catching

What energy is affected by velocity?

Kinetic

What energy is affected by height?

Gravitational Potential Energy

What energy is affected by stiffness?

Strain energy

How do you find gravitational potential energy?

Don’t need velocity

How do you find kinetic energy?

Don’t need height

What happens to the object when it’s moving up towards the apex?

Kinetic decreases, GPE increases

Pole Vault Picture, Which line is gravitational?

C is gravitational

During the ascending phase of the bench press the pectorals produce ___ work to ___ the total mechanical energy.

Positive, increase

During the descending phase of the bench press the pectorals produce ___ work to ___ the total mechanical energy.

Negative, decrease

What type of work occurs during a follow-through phase of a bat swing and what does it do?

Negative work, Absorbs

How do you calculate power?

Power = Work/Time, Force x Displacement/Time