Glossary
Acceleration ($\vec{a}$)
The rate at which an object's velocity changes over time, including changes in speed or direction. It is a vector quantity measured in meters per second squared (m/s²).
Example:
A car speeding up from a stop sign experiences positive acceleration, while a car braking experiences negative acceleration (deceleration).
Applied Force ($\vec{F}_{app}$)
Any external push or pull exerted on an object by a person or another object.
Example:
If you are pushing a shopping cart, the force you exert on the cart is an applied force.
Free-Body Diagrams (FBDs)
Visual representations used to analyze forces acting on a single object, showing all external forces as labeled vectors originating from the object.
Example:
Before solving a problem involving a block sliding down a ramp, drawing a free-body diagram helps identify and visualize the gravitational, normal, and frictional forces acting on the block.
Friction ($\vec{F}_f$)
A force that opposes motion or attempted motion between two surfaces in contact, acting parallel to the surfaces.
Example:
When you try to push a heavy couch across the floor, the friction between the couch and the floor makes it difficult to move.
Gravity ($\vec{F}_g$)
The force of attraction between any two objects with mass, commonly referring to the force exerted by a planet on an object near its surface, always pointing downwards.
Example:
When you drop a pen, the force of gravity pulls it directly towards the Earth's center.
Mass (m)
A scalar measure of an object's inertia, representing its resistance to changes in motion (acceleration). It is measured in kilograms (kg).
Example:
It's much harder to push a car (high mass) to get it moving than it is to push a bicycle (low mass).
Net Force ($\vec{F}_{net}$)
The vector sum of all individual forces acting on an object. It determines the object's acceleration according to Newton's Second Law.
Example:
If you push a box with 10 N to the right and a friend pushes it with 5 N to the left, the net force on the box is 5 N to the right.
Newton's Second Law
A fundamental principle stating that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. It is mathematically expressed as $\vec{F}_{net} = m\vec{a}$.
Example:
When a soccer player kicks a ball, the harder they kick (more force), the greater the ball's acceleration will be, assuming the ball's mass remains constant.
Normal Force ($\vec{F}_N$)
The component of a contact force exerted by a surface on an object that is perpendicular to the surface and prevents the object from passing through it.
Example:
When a book rests on a table, the table exerts an upward normal force on the book, balancing the force of gravity.
Tension ($\vec{T}$)
A pulling force transmitted axially through a string, rope, cable, or similar one-dimensional continuous object, always acting along the length of the object.
Example:
When you pull a wagon with a rope, the tension in the rope is the force pulling the wagon forward.