Khan Academy Exercises and Videos

Resonance

2026-08-12T02:40:45.919817

The natural frequency of a system is the frequency at which the system will oscillate when it is displaced from its equilibrium position. In the presence of a sinusoidal external force, a system may exhibit resonance. Resonance occurs when an external force is exerted at the natural frequency of the oscillating system. Resonance increases the amplitude of oscillating motion.

Worked example: Rewriting and solving equations by completing the square (IMRA 2026 publisher-initiated change)

2026-08-11T21:10:42.333577

Rewrite and solve quadratic equations by completing the square. IMRA 2026 publisher-initiated change

Volcanoes - Introductory

2026-08-11T07:20:42.258485

Volcanoes - Introductory

Resistors in Series

2026-08-10T10:50:43.838433

This video explains series resistors in electric circuits. Learners will understand that resistors are components that oppose the flow of electric current. In a series circuit, resistors are connected one after another in a single path.

Resistivity & conductivity IN

2026-08-10T10:50:43.838433

The video explains the relationship between resistance, resistivity, and conductivity. According to Ohm's law, resistance is defined as the ratio of voltage to current. To change a resistor's resistance, its physical properties, such as length, area of cross section and resistivity need to be changed. Resistivity is a material property representing its natural resistance to current flow and the unit for resistivity is ohm-meters. Conductivity is the inverse of resistivity, indicating how easily current flows.

Types of Muscles IN

2026-08-10T10:20:51.051442

There are three main types of muscles found in the human body. Skeletal muscles are commonly found throughout the body, often attached to bones via tendons and help in movement. Cardiac muscles are found only in the heart. Smooth muscles are located in the walls of hollow organs (like the stomach) and blood vessels.

Cell parts and their functions IND

2026-08-10T10:20:51.051442

The video explains various cell structures and their unique functions. The cell membrane regulates the entry and exit of substances in the cell. Inside the cell is cytoplasm which is a jelly-like substance containing an internal structural network and cell organelles.

Introduction to cells IN

2026-08-10T10:20:51.051442

This video introduces cells as the fundamental building blocks of life. The cell membrane separates the components of cells from the outside. he cytoplasm includes everything inside the cell membrane. The fluid part of it is called cytosol. Ribosomes synthesize proteins from RNA. Most cells store genetic information in the form of DNA. Based on presence or absence of a well-defined nucleus and membrane-bound organelles, cell can be categorised as eukaryotic or prokaryotic cells, respectively.

Units IND

2026-08-10T10:20:51.051442

Units are used to describe various physical properties, including position, length, mass, etc. To avoid confusion and accidents, scientists all over the world use a standardized system called International System of Units (SI units).

Modeling spring-mass oscillators

2026-08-07T23:00:44.279289

Simple harmonic motion (SHM) can be modeled mathematically as a second-order differential equation derived using Newton’s second law. The solution to this differential equation is the object’s position as a function of time, which is sinusoidal. The position function can be differentiated with respect to time to find the object’s velocity and acceleration functions, which are also sinusoidal.

Modeling pendulums

2026-08-07T23:00:44.279289

A physical pendulum is a rigid system that undergoes oscillation about a fixed axis. For small amplitudes of motion, the period of a physical pendulum is derived from the application of Newton’s second law in rotational form. A simple pendulum is a special case of physical pendulums in which the object can be modeled as a point mass hanging from the pivot point. A torsion pendulum involves a twisted wire or other material that behaves analogously to a spring. If the wire exerts a restoring torque proportional to its angle of twist, simple harmonic motion can result.

Locating information across a document

2026-08-07T11:20:58.434105

Workplace documents (manuals, procedures) and Written materials (forms). Learners find the correct section of a repair manual for one part and locate the right field on a leave-request form in a business process outsourcing (BPO) or call center.

Deciding when to ask for clarification

2026-08-07T11:20:58.434105

Communication context: classroom and training environment discussions. Written materials: short instructions that contain a confusing or missing step on purpose. Learners judge whether they understand, decide whether to ask, choose a clear question, and answer questions back appropriately. The trainer is present to guide the discussion.

Organizing information from different parts of one document

2026-08-07T11:20:58.434105

Written materials: one workplace document (for example a single report or notice) that holds pieces of the answer in different sections — a header, a body, and a labeled section. Text types: a short report with separate, clearly labeled sections. Tasks: a routine training activity where learners gather facts from each section of the same document and sort them into a given order or grouping. The grouping is set for them, so the activity stays supported and routine. (Combining information across two or more separate sources is reserved for Literacy 2B.)

Examining information to solve a routine problem

2026-08-07T11:20:58.434105

Workplace documents (manuals, work instructions) and Tasks (routine workplace tasks). Learners break down a troubleshooting table, match the problem to a cause, and relate it to the matching fix step. Working across sources: the problem requires comparing and reconciling two written sources (for example the troubleshooting table and the maintenance log), so the learner lines up what each says before deciding the cause and the fix. This gives the defining 2B multi-source skill (PC 2.2) a second point of evidence beyond L11.

Describing how pieces of information connect

2026-08-07T11:20:58.434105

Workplace documents (procedures, reports) and Visual information (tables). Learners explain how a 'wait 30 minutes' step links to a 'do not open the oven' warning, and how a stock table column links to its heading.

Write a short message for a work need

2026-08-07T11:20:58.434105

Text types: short messages and simple notices the learner writes from a given example. Communication context: a simulated workplace with a clear reason to write. Tasks: a basic workplace simulation where the learner plans the message, writes it, and checks that it says one clear idea. The purpose and audience are given, so the task stays supported.

Explaining written workplace instructions

2026-08-07T11:20:58.434105

Workplace documents (work instructions, procedures) and Tasks (routine workplace tasks). Learners restate each step of a clinic surface-cleaning procedure and a store closing checklist in plain words. This lesson sits at the 2A level on purpose: it is included to bridge and scaffold learners from 2A into 2B.

Explaining the main idea of a short text

2026-08-07T11:20:58.434105

Text types: a short report, a posted notice, and a short instruction paragraph. Tasks: a guided training activity where learners say or write the main idea in one sentence and name a supporting detail. Single short source with teacher support.

Communicating task information clearly

2026-08-07T11:20:58.434105

Communication context (workplace discussions, team meetings) and Tasks (routine workplace tasks). Learners report the status of a task at a kitchen shift handover and ask a clear question from the written job order at a construction toolbox meeting.

Principles of prevention

2026-08-13T08:39:32.000000

Let's answer some questions!

Principles of treatment

2026-08-13T08:03:41.000000

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Organ-specific and Tissue-specific manifestations

2026-08-13T07:54:20.000000

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PhET challenge: Conservation of energy

2026-08-13T02:33:19.000000

Use a PhET simulation to test your knowledge of conservation of energy with this set of free, standards-aligned practice questions.

Kinematic vectors in 2D

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Apply your knowledge of kinematic vectors in 2D in this set of free practice exercises.

Rotational kinetic energy and rolling

2026-08-13T02:24:10.000000

Check your understanding of rotational kinetic energy and rolling in this set of free practice questions.

Vocabulary Practice

2026-08-12T18:04:39.000000

Vocabulary practice for grade 8

Means of spread

2026-08-12T17:17:05.000000

Let's answer some questions!

Divide multi-digit numbers by 6, 7, 8, and 9 (remainders)

2026-08-12T16:45:15.000000

Practice dividing 2-, 3-, and 4-digit numbers by a 1-digit number. Divisors are 6, 7, 8, and 9. Quotients include remainders.

Infectious Diseases and Infectious agents

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Infectious and non-infectious causes

2026-08-12T14:14:35.000000

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Disease and its causes

2026-08-12T13:17:29.000000

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The Significance of Health

2026-08-12T12:50:28.000000

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Simple pendulums

2026-08-12T12:27:58.000000

Apply your knowledge of simple pendulums in this set of free practice questions.

Introduction to Antibiotics

2026-08-12T12:02:59.000000

Let's answer some questions!

Trigonometric ratios in right triangles

2026-08-12T06:48:34.000000

Given the side lengths of a right triangle, find the sine, cosine, or tangent of one of the acute angles.

Word problems: write quadratic equations

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Let's try to express some real-world scenarios using quadratic equations

Systems of equations with elimination

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Solve systems of equation with one-step elimination (e.g., x-values or y-values cancel each other out).

Systems of equations with substitution

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Solve systems of equations where one of the equations is solved for one of the variables.

Number of solutions to a system of equations graphically

2026-08-12T05:29:31.000000

Determine the number of solutions of a given system of equations by considering its graph.