What is a Force?
A force is a push or pull on an object interacting with another object. Forces are represented as vectors, as they have both direction and size. The base unit for force is the Newton(N).
There are two categories of forces:
Contact Forces, including:
There are two categories of forces:
Contact Forces, including:
- Applied Force
- Normal Force
- Tension Force
- Friction Force
- Spring Force
- Gravity
System Schemas, Force Diagrams, and Force Tables
Forces are represented using different types of diagrams/tables. Here are examples of each listed above, and what information they provide:
(from OneNote)
(from OneNote)
Force Models Representing Motion:
An object is either moving at a constant velocity (including 0m/s or stationary) or accelerating. Force models provide a visual of forces on an object, and because of the direction and length of the vectors, we can see unbalanced or balanced forces. Thus, motion is represented in force diagrams because the net force on an object depicted in these show whether or not an object is stationary or at a constant velocity, or accelerating.
An object is either moving at a constant velocity (including 0m/s or stationary) or accelerating. Force models provide a visual of forces on an object, and because of the direction and length of the vectors, we can see unbalanced or balanced forces. Thus, motion is represented in force diagrams because the net force on an object depicted in these show whether or not an object is stationary or at a constant velocity, or accelerating.
Newton's First Law (Inertia)
An object moving at a constant velocity will continue to move at a constant velocity unless the forces acting upon it are unbalanced.
As the mass of an object increases, the inertia of object increases.
As the mass of an object increases, the inertia of object increases.
Newton's Second Law and Force Calculations
The acceleration of an object is dependent on its mass and the forces acting on it:
ΣF=m*a
Force Calculations use equations, including Newton's second law, to determine different variables of an object, like the forces acting on it, its mass, acceleration, or specific force coefficients. Important equations are listed below:
ΣF=m*a
Force Calculations use equations, including Newton's second law, to determine different variables of an object, like the forces acting on it, its mass, acceleration, or specific force coefficients. Important equations are listed below:
- ΣF=m*a - find net force of an object (Newton's second law)
- F(gravity)=m*g - to find force of gravity/weight on an object
- F(spring)=-k*Δx - to find spring force or spring constant (k) on an object (AKA Hooke's Law)
- F(friction)=µ*F(normal) - to find friction force or friction coefficient (µ)
Newton's Third Law
Every force exerted on one object by another is in a pair with another force equal in magnitude and opposite in direction from the one object on the other.
Third law pairs are not balanced forces-- they are one actual force on two objects, interacting with each other.
Third law pairs are not balanced forces-- they are one actual force on two objects, interacting with each other.
Solving Force Problems
Here is an example force problem with motion:
(from OneNote)
(from OneNote)