Glossary
Archimedes' Principle
States that the buoyant force on a submerged or floating object is equal to the weight of the fluid displaced by the object.
Example:
A ship floats because the weight of the water it displaces, as described by Archimedes' Principle, is equal to the ship's total weight.
Buoyant Force
The upward force exerted by a fluid on an object that is submerged or floating, opposing the object's weight.
Example:
A boat floats on water because the buoyant force from the water supports its weight.
Coefficient of Friction (μ)
A dimensionless scalar value that describes the ratio of the force of friction between two bodies and the normal force pressing them together.
Example:
A high coefficient of friction between tires and the road allows a car to brake quickly without skidding.
Conservative Forces
Forces for which the work done in moving an object between two points is independent of the path taken, allowing mechanical energy to be stored as potential energy and recovered.
Example:
Gravity is a conservative force because the work done by gravity on an object only depends on its initial and final heights, not the path it took.
Contact Forces
Forces that arise from the electromagnetic interactions between atoms when two objects physically touch, fundamental to understanding how objects interact.
Example:
When you push a shopping cart, the force you apply is a contact force.
Density (ρ)
A measure of mass per unit volume of a substance, crucial for determining whether an object will float or sink in a fluid.
Example:
A block of wood floats in water because its density is less than that of water.
Free Body Diagram (FBD)
A visual representation used to analyze forces acting on a single object, showing all forces as vectors originating from the object's center of mass.
Example:
Before solving a problem about a block sliding down a ramp, drawing a Free Body Diagram helps identify all forces like gravity, normal force, and friction.
Friction
A force that opposes relative motion or the tendency of motion between two surfaces in contact. It can be static (preventing motion) or kinetic (opposing sliding motion).
Example:
When you try to slide a heavy box across the floor, friction makes it difficult to move.
Hooke's Law
A principle stating that the force needed to extend or compress a spring by some distance is directly proportional to that distance, expressed as F = -kx.
Example:
According to Hooke's Law, doubling the stretch of a spring will double the force it exerts.
Kinetic Friction
The force that opposes the relative sliding motion between two surfaces that are already in motion, typically less than the maximum static friction.
Example:
When a hockey puck slides across ice, kinetic friction gradually slows it down.
Non-Conservative Forces
Forces for which the work done depends on the path taken, typically converting mechanical energy into other forms like heat or sound, leading to energy dissipation.
Example:
Air resistance is a non-conservative force because it dissipates mechanical energy as heat, causing a falling object to reach terminal velocity.
Normal Force
The component of a contact force exerted by a surface on an object, acting perpendicular to the surface, preventing the object from falling through it.
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, representing the force required to stretch or compress the spring by a unit distance.
Example:
A car's suspension system uses springs with a high spring constant to absorb bumps effectively.
Spring Force
The restorative force exerted by a spring when it is stretched or compressed from its equilibrium length, always acting to return the spring to equilibrium.
Example:
When you compress a toy dart gun, the spring force builds up, ready to launch the dart.
Static Friction
The force that opposes the initiation of motion between two surfaces in contact when there is no relative motion, varying up to a maximum value.
Example:
The static friction between your shoes and the ground allows you to push off and walk without slipping.
Tension
The pulling force exerted by a rope, string, or cable when it is pulled taut, always acting along the direction of the rope.
Example:
A rock climber relies on the tension in their rope to prevent a fall.