Bioenegetics Forces

What is Force?

Effect that one object has on another

• A push or pull exerted by one object on another object

• Required to change the state of motion of an object

• Causes Object to accelerate

• Force (cause) → Acceleration (effect)

F=ma

F= force; m= mass of the object; a= acceleration

Force Units

Units: Newton (N)

1N =amount of force needed to accelerate a 1kg object by 1 m/s²

Weight is a force, has to be in N

weight = mass x gravity (gravity = -9.81 m/s²

Characteristics of force

Force is a vector quantity

• both magnitude (size) and direction (orientation)

Magnitude of vector

size of the push or pull (longer mag = greater force/vector)

Direction of vector

Line of action: which way a force is pushing/pulling

point of application of a vector

Where the push/pull is applied on the object Scalar

Scalar

A quantity that is defined by its size/magnitude

ex: mass, time, speed, distance, temp,etc

Just magnitude no direction

Vector

A quantity that is defined by its size/magnitutide AND direction

Represented as arrows: length= size/magnitude, pointing= direction

ex: velocity, acceleration, “force,” etc

Distance

How much ground an object has covered (Scalar)

Displacement

Overall change in position (Vector)

consider start position & end position

Speed

How fast SCALAR

Velocity

The rate at which an object changes position VECTOR

ex: 65mph, North

Internal force

Act within the object or system ( human body)

Hold the object together

ex; muscle tension,ligament tension, bone compression (external forces become greater)

External Forces

Act on an object as a result of interaction with enviornment

Contact forces: occur from objects coming into contact (ground reaction force, friction force)

Non-contact forces: occur even if objects are not in contact (gravity, magnetic, electrical)

Normal contact Force

Perpendicular to the two objects in contact

Parallel (tangential) contact force

Parallel to contacting surfaces of two objects

Friction force formula

F= uR

F= friction force

u= coefficient of friction

R= normal contact force

Non-Contact Forces: forces that occur even if objects are not in

contact

• Weight – force of gravity acting on an object

• W = mg

• W = weight in newtons

• m = mass in kilograms (kg)

• g = acceleration due to gravity = 9.81 m/s2 downward

Net Force?

sum of all external forces acting on one object, also called

resultant force

• Not simply summing all external force magnitudes

− Must account for the direction of each force

• What is the effect of two 100N forces on an object?

− Depends on the specified direction of the two forces

Vector Composition

The process of determining a single vector (force) from two or more vectors

(forces) by vector addition

• Finding the resultant vector or net vector

Resultant vector

a single vector that represents the combined effect of two or

more vectors

Vector Resolution

• The process of breaking a single vector into two or more component vectors

• Typically, a vector is resolved into horizontal (x-axis) and vertical (y-axis) components

• Ex) a force of 10N at 30° above the horizontal

• Fx = 10cos30°

• Fy = 10sin30°

Head-Tail method

Rearrange to link head and tail

Colinear Vectors

Two or more vectors that have the same line of action

− Vectors are acting “parallel” to each other

Simply sum up the values to get the magnitude of the resultant vector

Concurrent Vectors

Vectors that do not act along the same line of action