Glossary
Coefficient of Friction (μ)
A dimensionless value that quantifies the amount of friction between two surfaces, representing the ratio of the frictional force to the normal force.
Example:
Ice has a very low coefficient of friction, which is why it's so slippery.
Contact Forces
Forces that arise when two objects are in direct physical contact, resulting from interactions between their particles.
Example:
When you kick a soccer ball, the force your foot exerts on the ball is a contact force.
Free-Body Diagram
A visual representation that isolates an object and shows all external forces acting upon it as vectors.
Example:
Drawing a free-body diagram is the first step to solving complex problems involving multiple forces on an object.
Friction
A force that opposes the motion or attempted motion between two surfaces in contact.
Example:
The friction between a car's tires and the road allows it to accelerate and brake safely.
Hooke's Law
A principle stating that the force exerted by a spring is directly proportional to its displacement from equilibrium, with the force acting in the opposite direction of the displacement.
Example:
According to Hooke's Law, if you stretch a spring twice as far, it will pull back with twice the force.
Inclined Plane
A flat, sloped surface that allows objects to be moved between different heights, requiring the resolution of forces into components parallel and perpendicular to the slope.
Example:
Pushing a heavy box up a ramp, which is an inclined plane, is easier than lifting it straight up.
Kinetic Friction
The frictional force that acts on objects in motion, opposing their sliding movement, and is typically constant.
Example:
A sled sliding down a snowy hill experiences kinetic friction that slows it down.
Normal Force
The force exerted by a surface on an object resting on it, always acting perpendicular to the surface.
Example:
A book resting on a table experiences an upward normal force from the table, balancing its weight.
Spring Constant (k)
A measure of the stiffness of a spring, indicating how much force is required to stretch or compress it by a unit distance.
Example:
A car's suspension system uses springs with a specific spring constant to provide a smooth ride.
Spring Force
The restorative force exerted by a spring when it is compressed or stretched, always acting to return the spring to its equilibrium position.
Example:
When you jump on a trampoline, the upward push you feel is the spring force from the stretched fabric.
Static Friction
The frictional force that acts on objects at rest, preventing them from starting to move, and can vary up to a maximum value.
Example:
It's hard to push a heavy box from rest because of the strong static friction between it and the floor.
Tension
The force transmitted through a rope, string, or wire when it is pulled taut, acting along the direction of the material.
Example:
A tug-of-war team applies tension to the rope, pulling against their opponents.
Weight (Gravity)
The force exerted by gravity on an object's mass, always directed vertically downwards towards the center of the Earth.
Example:
An apple falling from a tree is pulled down by its weight due to Earth's gravity.