Physics: Motion, Forces, Energy, and Simple Machines

A comprehensive set of vocabulary flashcards covering motion, Newton's laws of motion, energy types, conservation of energy, and simple machines based on the lecture transcript.

Reference point

The starting point you use to describe the motion or the position of an object.

Position

An object’s distance and direction from a reference point.

Motion

The process of changing position.

Displacement

The difference between the initial position and the final position of an object.

Speed

A measure of the distance an object travels per unit of time, usually measured in $\text{m/s}$.

Constant speed

The rate of change of position in which the same distance is traveled each second.

Instantaneous speed

The speed of an object at a specific instant in time.

Average speed

Total distance traveled divided by the total time needed to travel that distance.

Velocity

The speed and direction of a moving object.

Acceleration

A measurement of the change in velocity during a period of time, calculated as $a = \frac{v_{final} - v_{initial}}{t}$.

Inertia

A property of matter that resists change in motion and is proportional to its mass.

Force

A push or pull interaction between two objects.

Contact force

A push or pull on one object by another that is touching it.

Noncontact force

A force an object can exert on another object without touching it, such as gravity or electric force.

Mass

The amount of matter in an object, measured in units like $\text{kg}$.

Weight

The gravitational force exerted on an object.

Friction

The force that resists the motion of two surfaces that are touching each other.

Static friction

The force that resists an applied force that would normally cause an object to start moving.

Sliding friction

The force that opposes the motion of surfaces sliding against each other.

Fluid friction

Friction between a surface and a fluid, such as air resistance.

Net force

The combination of all the forces acting on an object.

Balanced forces

Forces acting on an object that combine and form a net force of zero.

Unbalanced forces

Forces acting on an object that combine and form a net force that is not zero, causing acceleration.

Circular motion

Any motion in which an object is moving along a curved path.

Centripetal force

A force that pulls an object toward the center of a curve and keeps it in orbit.

Force pair

The forces two objects apply to each other, which are equal in strength and opposite in direction.

Momentum

A measure of how hard it is to stop a moving object, calculated as $p = m \times v$.

Law of conservation of momentum

The principle that the total momentum of a group of objects stays the same unless outside forces act on the objects.

Energy

The ability to cause change.

Kinetic energy

Energy due to motion, which depends on the mass and velocity of a moving object.

Potential energy

Stored energy due to the interactions between objects or particles.

Elastic potential energy

Energy stored in objects that are stretched or compressed.

Chemical potential energy

Energy stored in the chemical bonds between atoms.

Gravitational potential energy

The energy an object possesses because of its position in a gravitational field, typically defined by height and weight.

Work

The transfer of energy that occurs when a force is applied over a distance, calculated as $W = F \times d$.

Law of conservation of energy

Energy can be transformed from one form into another or transferred from one region to another, but it cannot be created or destroyed.

Mechanical energy

The total energy of an object due to large-scale motions and interactions, equal to the sum of kinetic and potential energy.

Thermal energy

Energy due to the motion of particles that make up an object.

Electric energy

Energy carried by an electric current.

Radiant energy

Energy that electromagnetic waves carry.

Nuclear energy

Energy that is stored in the nucleus of an atom.

Nonrenewable energy resource

An energy resource that is available in limited amounts or that is used faster than it is replaced in nature.

Renewable energy resource

An energy resource that is replaced as fast as, or faster than, it is used in nature.

Fossil fuels

Remains of ancient organisms that can be burned as an energy source, such as coal, oil, and natural gas.

Inexhaustible energy resource

An energy resource that cannot be used up, such as solar or wind energy.

Biomass

Organic material, such as manure or plant matter, that is often burned as fuel.

Power

The rate at which work is done, calculated as $P = \frac{W}{t}$.

Simple machine

A mechanical device that changes the direction or magnitude of a force and does work using only one movement.

Compound machine

A combination of two or more simple machines that work together to perform a task.

Mechanical advantage

The ratio of output force produced to input force applied, represented as $MA = \frac{F_{out}}{F_{in}}$.机关

Efficiency

The ratio of output work to input work, calculated as $\text{Efficiency} = \frac{W_{out}}{W_{in}} \times 100\%$.机关

Lever

A simple machine made up of a bar that pivots, or rotates, about a fixed point called a fulcrum.

Fulcrum

The fixed point about which a lever pivots.

Wheel and axle

A simple machine consisting of an axle attached to the center of a wheel, where both rotate together.

Inclined plane

A flat, sloped surface (ramp) used to help raise or lower objects with less force.

Wedge

A sloped surface that moves, typically used to split or lift objects.

Screw

An inclined plane wrapped around a cylinder used to hold objects together or lift materials.

Pulley

A simple machine consisting of a grooved wheel with a rope or cable wrapped around it.

Gear

A wheel and axle with teeth around the wheel that interlock with other gears to change motion or force.