Mechanical Work & Energy

What is Mechanical Work (W)?

- product of a force or torque applied to the object and the displacement caused by the force

When is mechanical work produced?

- when force or torque causes object to move/deform

How do you find linear work?

- average force x displacement (finished position - starting position)

How do you find angular work?

- average torque x angular displacement

What happens with mechanical work if force/torque and displacement are in the same direction? (what is the muscle contraction)

- mechanical work produced is positive (concentric)

What happens with mechanical work if force/torque and displacement are in the opposite direction? (what is the muscle contraction)

- mechanical work produced is negative (eccentric)

What is mechanical energy?

- the energy the objects possess due to motion or position in space (always positive)

What are the forms of mechanical energy?

- kinetic energy
- potential energy

How do you find total mechanical energy?

- kinetic energy + potential energy

What is kinetic energy?

- energy possessed by a moving object

What is kinetic energy determined by?

- mass of object
- velocity of object

How do you find kinetic energy?

- ½ x mass x velocity²

What is potential energy?

- energy that is stored in an object due to its height or deformation

What are the forms of potential energy?

- gravitational potential energy
- strain energy

What is gravitational potential energy?

- potential energy an object possesses due to its height

What is gravitational potential energy determined by?

- mass of object
- height of object

How do you find gravitational potential energy?

- mass x gravitational acceleration (9.81) x height

What is strain energy?

- potential energy an object possesses due to deformation

When is strain energy stored in the object?

- object is being compressed
- object is being elongated

How do you find strain energy?

- ½ x stiffness x deformation²

What is the Law of Conservation of mechanical energy?

- when gravity is the only external force acting on the object, total mechanical energy of object remains constant

How are work and energy related to each other?

- work is a way to transfer energy between objects
- energy is used to produce work

How is work and energy related to each other?

- increased work, increased energy objects have
- increased energy, increased capacity to produce work

What is the work-energy relationship?

- work produced on an object is equal to the change in mechanical energy of the object

What happens when an object produce mechanical work on another object?

- energy is being transferred between them (equal to amount of mechanical work produced)

How does ±/- work affect mechanical energy?

- + work increases object’s mechanical energy (work will transfer energy to other object)
- - work decreases object’s mechanical energy (work will absorb other objects energy)

What does the work-energy relationship allow us to calculate?

- the force applied to the object by calculating change in total mechanical energy
- F = total mechanical energy / displacement (change)

What is power?

- a rate at which the mechanical work is produced
- more work produced, higher power produced

How to find power?

- power = mechanical power / time

How can you produce higher power?

- produce high force at high velocity
- improve muscle strength will increase power production capacity

What is the relationship between power and work?

- when work is positive, power is positive (muscle contracting concentrically)
- when work is negative, power is negative (muscle contracting eccentrically)

On a graph what is the area under the power curve?

- work produced (mechanical energy transferred