2. Force Flashcards
What do scales measure?
a) Mass
b) Weight
c) Force
d) All of the above
b
What is a Force?
A force is a push or pull
A force attempts to create a change (in motion)
What is the effect of the force dependent upon?
- The magnitude of the Force
- The relative position of the force
- The point of Application
- F on side = Translational & Rotational
- F on Center = Translational
What is a Reaction Force?
Forces come in pairs
Force exerted by one object on another is matched by an equal but oppositely directed force
What is the The SI unit of measurement for force?
the newton (N)
Named in honour of the English scientist and mathematician, Sir Isaac Newton
What is One Newton Force defined as?
One newton of force is defined as:
○ The force required to accelerate a 1 kg mass 1 m/s2
○ 1 N = 1 kg * m/s2
○ Force (F) = mass (m) x acceleration (a)
○ F = ma (2nd Law)
What is a Vector?
A force is a vector
A quantity having direction as well as magnitude
How do you fully describe a Force?
To fully describe a force, you must identify its:
Orientation (direction)
■ + or – sign
■ Angle in degrees (º)
Size (magnitude)
■ Number value (0.0)
What is an internal force?
Internal forces act within the object or system whose motion is being investigated
In the human body:
● Muscles pull on tendons, which pull on bones
● Bones push on cartilage, which pushes on other cartilage and bones
Muscle forces can produce motions of the body’s limbs
■ Internal forces are incapable of producing changes in the motion of the entire body
Internal forces may be important when examining the nature and causes of injury
What is an External Force?
What are its 2 Classes?
External forces act on an object as a result of its interaction with the surrounding
■ The body changes its motion only if it can push or pull against some external object
External forces can be classified as:
contact or noncontact forces
What are contact forces?
Contact forces occur b/w objects in contact with one another
● Solid contact forces exist between two physical objects
● Air resistance and water are examples of fluid contact forces
What are non-contact forces?
Noncontact forces can occur even if the objects are not touching
● Gravity, magnetic forces, and electrical forces are examples Classifying Forces
What is Gravitational Attraction?
● The force of gravity is the only noncontact force considered in sport and exercise
● The force of gravity accelerates an object downward at a rate of 9.81 m/s2 (or -9.81 m/s2)
● This acceleration is called gravitational acceleration or the acceleration due to gravity (ag)
What is “weight”?
The force of gravity acting on an object is defined as weight
○ Weight (wt) = mass (m) x acceleration due to gravity (ag)
○ wt = mag
○ -9.81 N = 1 kg / -9.81 m/s2
What is Dynamography?
The measurement and recording of forces and pressure.
It’s often used in biomechanics to measure forces exerted by the body during activities like walking or running
dynamography
What is a Strain Gauge?
A strain gauge is a device that measures force or pressure by detecting deformation in an object.
It consists of a wire attached to two pads. When the object bends or deforms, the resistance of the wire changes.
The degree of wire bending is related to the force applied, allowing the strain gauge to measure that force.
dynamography
What is a Load Cell?
A load cell is a transducer used to convert force into electrical signals.
It typically consists of a spring element encased in metal. As more force is applied to the load cell, the spring element deforms, and this deformation changes the electrical signal proportionally.
The more force applied, the greater the change in the signal, allowing precise force measurement.
What are Force Platforms?
Load cells are often put on force platforms (or force plates)
Force platforms (or force plates) are instruments designed to measure the ground reaction forces (GRF) generated by a body either standing on or moving across the platform
What are the ground reaction forces (grf) when walking and when running?
GRF are ~1 to 1.2x body weight when walking
GRF ~3 to 5x body weight when running
