FORCE

(definition)

FORCE DIAGRAM

(definition)

Definition: Amount of matter in an object.

Symbol: m

Units: kilograms (kg)

Definition: Acceleration of an object due to the Force that Earth exerts on the object.

Slope of the F_EonO vs. Mass graph

Always 9.8 m/s² on Earth

Symbol: g

Units: m/s² 

Definition: Force exerted by Earth on any object.

Symbol: F_EonO

Direction: Always down towards the center of Earth

Units: N (Newtons)

FORCE OF EARTH

(math model)

Definition: Force requiered to stretch a spring by one meter ( 1 m )

Slope of the F_SonO vs. DL graph

Symbol: k

Units: N/m

ELONGATION

Definition: How much a spring stretches or compresses beyond its relaxed length.

Symbol: DL

Units: meters (m)

Definition: Force exerted by a spring on any object.

Symbol: F_SonO

Direction: Always in the direction of the spring.

Units: N (Newtons)

FORCE OF THE SPRING

(math model)

NORMAL FORCE

Definition: Force exerted by any surface that supports an object.

Symbol: F_N

Direction: Always perpendicular to the surface (90° angle)
 

Units: N (Newtons)

TENSION FORCE

Definition: Force exerted by any string, rope, thread, lasso, etc.

Symbol: F_T

Direction: Always in the direction of the string.

Units: N (Newtons)

WEIGHT

(definition)

Magnitude (number) of the Force that Earth exerts on an object.

Example: the mass of an apple is 0.5 kg.

F_EonA = - 4.9 N

Weight = 4.9 N

HEAVY

(definition)

How humans perceive the force of Earth on an objects.

An object with a big mass will feel heavier than an object with a small mass (it will feel lighter).

MASS is the amount of matter in an object (measured in kg).

WEIGHT is how much force Earth exerts on that mass (measured in N).

All forces are balanced

The objects moves with constant velocity (including v = 0 m/s)

The acceleration of the object is 0 m/s2

Definition: Sum of all objects exerted on an object.

Symbol: SF

Direction: Always in the direction of the unbalanced force

Units: N (Newtons)

• Unless an unbalanced force is exerted on an object. The object will continue moving with constant velocity.

The acceleration of an object is directly proportional to the acceleration of the object. 

The acceleration of an object is inversely proportional to the mass of the object.  

Newton’s second law is a cause/effect relationship because an unbalanced force will cause an acceleration (no the other way around).

When two objects interact, object A exerts a force on object B. In turn, object B exerts a force on object A.

These two forces are equal in magnitude, but opposite in direction. 

Definition: Ratio between two forces F_K & F_N.

Slope of the F_K vs. F_N graph

Symbol: µ_K

Units: (no units)

Definition: Force exerted by any surface that opposes the motion of the object.

Symbol: F_K

Direction: Always parallel to the surface (0° angle)

Units: N (Newtons)