DOST-SEI Mechanical Reasoning Reviewer: Electrical Systems & Circuits

TEACHER ABI · DOST-SEI MECHANICAL REASONING

Electrical Systems & Circuits

Trace the path first. Then decide what happens to current, voltage, resistance, and bulb behavior when a circuit changes.

5–10 minute lesson27 original questionsCircuit reasoningSaves progress

LessonShortcutExamplesSkill CheckPracticeMasteryFAQ

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Start with the five-form Skill Check.

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Trace the complete conducting path

Closed vs open
Current needs a complete conducting path.

Series
One path; the same current passes through each series component.

Parallel
Separate branches provide separate paths.

Voltage
Potential difference drives charge through a circuit.

Resistance
At fixed voltage, greater resistance means smaller current: I = V/R.

Bulb failures
Retrace which complete paths remain after the failure.

DO IT FAST

PATH → BRANCH → CHANGE

PATH: is the loop complete? BRANCH: is the component on the only path or one of several paths? CHANGE: after a switch, bulb, or resistor changes, retrace the remaining circuit.

WORKED EXAMPLES

Five circuit relationships

Open switch: breaking the only path stops current in that loop.

Series bulbs: identical bulbs in one path carry the same current.

Parallel bulbs: opening one branch need not stop another intact branch.

Ohm's law: at fixed voltage, doubling resistance halves current.

Failure tracing: never assume one broken bulb turns everything off; inspect the topology first.

Common traps

Current is not “used up” by the first series component. A battery supplies potential difference, not a fixed current for every circuit. Parallel branches are not the same as extra components in series. For failure questions, redraw the remaining conducting paths.

FIVE-FORM SKILL CHECK

Can you transfer the idea across five forms?

This diagnoses your next practice step; it does not verify mastery.

CHOOSE YOUR PRACTICE

Practice at the level you need

FRESH MASTERY CHECK

Verify the competency

Mastery requires 5/5. An unsuccessful attempt loads a different set.

FAQ

Quick clarifications

Does current get used up by the first bulb?
No. In a steady series loop, the same current passes through each component.

If one bulb fails, do all bulbs always go out?
No. It depends on whether the failure breaks the only path or just one parallel branch.

Why is this Mechanical Reasoning?
DOST's own Mechanical Reasoning description explicitly includes electrical problems.

RELATED COMPETENCIES

Mechanical Reasoning sequence complete

Gears & Gear Trains · Belts, Chains, Racks & Connected Wheels · Levers, Torque & Balance · Pulleys & Mechanical Advantage · Wheels, Axles & Rotational Systems · Forces, Friction & Equilibrium · Motion, Energy & Mechanical Relationships · Fluids, Pressure & Hydraulic Systems · Heat, Sound & Everyday Physical Effects · Electrical Systems & Circuits

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DOST-SEI Mechanical Reasoning Reviewer: Heat, Sound & Everyday Physical Effects

TEACHER ABI · DOST-SEI MECHANICAL REASONING

Heat, Sound & Everyday Physical Effects

Trace everyday heat and sound effects: how thermal energy moves, why materials expand, how sound travels through matter, and how motion changes the pitch we hear.

5–10 minute lesson27 original questionsEveryday-physics reasoningSaves progress

LessonShortcutExamplesSkill CheckPracticeMasteryFAQ

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Start with the five-form Skill Check.

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Trace how heat or sound moves

Thermal conduction
Heat flows through a material from higher temperature toward lower temperature.

Thermal conductivity
A better conductor transfers thermal energy through itself more readily than a poorer conductor under comparable conditions.

Thermal expansion
Many solids expand when heated, which is why structures such as bridges need room for expansion.

Sound needs a medium
Ordinary sound is a mechanical wave. Its speed depends on the medium; in the familiar comparison it is generally fastest in solids and slowest in gases.

Pitch and frequency
Higher frequency means higher perceived pitch.

Doppler effect
Approaching sound sources are heard at a higher frequency; receding sources are heard at a lower frequency.

DO IT FAST

SOURCE → MEDIUM → EFFECT

SOURCE: identify what produces the heat or sound. MEDIUM: identify the material or medium carrying the effect. EFFECT: predict the temperature, expansion, speed, pitch, or observed change.

WORKED EXAMPLES

Five everyday relationships

1. Conductors: if equal blocks receive comparable heating, a material with greater thermal conductivity transfers heat through the block more readily.

2. Expansion gaps: a bridge segment needs room to expand when its temperature rises.

3. Sound media: sound propagation depends on how disturbances travel through the particles of the medium.

4. Lightning and thunder: seeing lightning before hearing thunder illustrates that light reaches you much faster than sound through air.

5. Moving siren: an approaching siren is heard at a higher pitch than the same siren moving away.

Common traps

Temperature is not the same as heat. Thermal conductivity describes how readily energy is conducted through a material; it does not by itself tell you which object initially contains more thermal energy. Sound does not travel through an ordinary vacuum. For the Doppler effect, keep the source's emitted frequency separate from the frequency heard by the observer.

FIVE-FORM SKILL CHECK

Can you transfer the idea across five forms?

This diagnoses your next practice step; it does not verify mastery.

CHOOSE YOUR PRACTICE

Practice at the level you need

FRESH MASTERY CHECK

Verify the competency

Mastery requires 5/5. An unsuccessful attempt loads a different set.

FAQ

Quick clarifications

Are heat and temperature the same?
No. Temperature describes thermal state; heat refers to energy transferred because of a temperature difference.

Can sound travel in space?
Ordinary sound needs a material medium, so it cannot propagate through a perfect vacuum.

Does an approaching siren actually change the frequency it emits?
The source can emit the same frequency while relative motion changes the frequency received by the listener.

RELATED COMPETENCIES

Continue Mechanical Reasoning

Gears & Gear Trains · Belts, Chains, Racks & Connected Wheels · Levers, Torque & Balance · Pulleys & Mechanical Advantage · Wheels, Axles & Rotational Systems · Forces, Friction & Equilibrium · Motion, Energy & Mechanical Relationships · Fluids, Pressure & Hydraulic Systems · Heat, Sound & Everyday Physical Effects · Electrical Systems & Circuits

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DOST-SEI Mechanical Reasoning Reviewer: Motion, Energy & Mechanical Relationships

TEACHER ABI · DOST-SEI MECHANICAL REASONING

Forces, Friction & Equilibrium

Read everyday force situations correctly: identify the forces, decide their directions, compare them, and determine whether an object stays at rest, moves at constant speed, or accelerates.

5–10 minute lesson27 original questionsMechanism-first SVG diagramsSaves progress

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Start with the five-form Skill Check.

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Track what changes

Distance vs displacement
Distance counts the path; displacement compares final and initial position with direction.

Speed vs velocity
Velocity includes direction. Turning changes velocity even at constant speed.

Acceleration
Acceleration means velocity changes: speeding up, slowing down, or turning.

Height and energy
For the same object, greater height means greater gravitational potential energy.

Projectile motion
Gravity changes vertical motion while ideal horizontal motion continues.

Rolling
Rolling combines translation and rotation; mass distribution affects rotational inertia.

DO IT FAST

STATE → CHANGE → RESULT

STATE: identify the starting motion or energy state. CHANGE: mark exactly what changes—speed, direction, height, time, or input. RESULT: follow the physical consequence without adding an unstated assumption.

WORKED EXAMPLES

Five relationships to recognize

Turning: same speed can still mean changing velocity because direction changes.

Height: the same object has greater gravitational potential energy at the higher point.

Equal-time marks: increasing gaps mean increasing speed; equal gaps mean constant speed.

Projectile: at the highest point, vertical velocity is momentarily zero but horizontal velocity remains in the ideal model.

Rolling: equal-mass, equal-radius objects can roll differently if their mass distributions differ.

Common traps

Same speed does not mean same velocity when direction changes. Distance and displacement differ when a path reverses. A projectile is not stopped at its highest point. The heaviest rolling object does not automatically arrive first.

FIVE-FORM SKILL CHECK

Can you transfer the idea across five forms?

This diagnoses your next practice step; it does not verify mastery.

CHOOSE YOUR PRACTICE

Practice at the level you need

FRESH MASTERY CHECK

Verify the competency

Mastery requires 5/5. An unsuccessful attempt loads a different set.

FAQ

Quick clarifications

Can acceleration happen without speeding up?
Yes. Changing direction changes velocity.

At the top of a projectile path, is it stopped?
No. Vertical velocity is momentarily zero, but horizontal velocity remains in the ideal model.

Does the heaviest rolling object always arrive first?
No. Ideal rolling can depend on rotational inertia and mass distribution.

RELATED COMPETENCIES

Continue Mechanical Reasoning

Gears & Gear Trains · Levers, Torque & Balance · Pulleys & Mechanical Advantage · Belts, Chains, Racks & Connected Wheels · Wheels, Axles & Rotational Systems · Forces, Friction & Equilibrium · Motion & Mechanical Relationships · Basic Electrical & Mechanical Systems

DOST-SEI Student HubFree 120-item Diagnostic

DOST-SEI Mechanical Reasoning Reviewer: Forces, Friction & Equilibrium

TEACHER ABI · DOST-SEI MECHANICAL REASONING

Forces, Friction & Equilibrium

Read everyday force situations correctly: identify the forces, decide their directions, compare them, and determine whether an object stays at rest, moves at constant speed, or accelerates.

5–10 minute lesson27 original questionsMechanism-first SVG diagramsSaves progress

LessonShortcutExamplesSkill CheckPracticeMasteryFAQ

Your reviewer status

Start with the five-form Skill Check.

QUICK REVIEW

Force questions become easier when you separate the forces

1. Weight points downward
Gravity pulls an object toward Earth. Near the surface, weight is W = mg.

2. Normal force is perpendicular
A surface pushes on an object perpendicular to the surface—not automatically upward.

3. Friction opposes relative slipping
Static friction prevents slipping when possible. Kinetic friction acts while surfaces slide.

4. Static friction adjusts
Before slipping, static friction matches the needed opposing force up to its maximum value.

5. Net force controls acceleration
Balanced forces give zero acceleration. Unbalanced forces produce acceleration in the net-force direction.

6. Equilibrium means zero net force
An object may be at rest or move at constant velocity while the net force is zero.

DO IT FAST

OBJECT → ARROWS → NET

OBJECT: isolate the object being asked about. ARROWS: identify gravity, normal force, friction, tension, pushes or pulls and their directions. NET: compare forces by direction. Zero net force means no acceleration; a nonzero net force points in the acceleration direction.

WORKED EXAMPLES

Read the interaction before calculating

1. Box on a level floor

If the box is at rest with no other vertical forces, the upward normal force balances its downward weight.

2. Static friction

A 20 N horizontal push does not automatically create maximum friction. If the box remains at rest, static friction is 20 N opposite the push.

3. Rough ramp

Gravity has a component down the ramp. Static friction acts up the ramp while preventing the block from sliding.

4. Constant-speed pull

Constant speed means zero acceleration, so the horizontal pull and friction are equal in magnitude and opposite in direction.

5. Stability

An object is more stable when the vertical line through its center of mass remains inside a wide base of support.

Common traps

“Moving means a force must point forward”: an object can move at constant velocity with zero net force. “Friction always equals μN”: static friction can be smaller than its maximum. “Normal force is always vertical”: it is perpendicular to the contact surface. “Friction always opposes motion”: more precisely, it opposes relative slipping or the tendency to slip at the contact. “Balanced forces mean no motion”: they mean no acceleration.

FIVE-FORM SKILL CHECK

Can you transfer the idea across five forms?

This diagnoses your next practice step; it does not verify mastery.

CHOOSE YOUR PRACTICE

Practice at the level you need

FRESH MASTERY CHECK

Verify the competency

Mastery requires 5/5. An unsuccessful attempt loads a different set.

FAQ

Quick clarifications

Is friction present if an object is not sliding?
It can be. Static friction acts when needed to prevent relative slipping.

Does zero net force mean zero velocity?
No. It means zero acceleration, so velocity stays constant.

On a ramp, which way does the normal force point?
Perpendicular to the ramp surface.

What determines when a block first starts sliding on a ramp?
In the idealized model, slipping begins when the required static friction reaches its maximum; the threshold depends on the coefficient of static friction.

RELATED COMPETENCIES

Continue Mechanical Reasoning

Gears & Gear Trains · Levers, Torque & Balance · Pulleys & Mechanical Advantage · Belts, Chains, Racks & Connected Wheels · Wheels, Axles & Rotational Systems · Forces, Friction & Equilibrium · Motion & Mechanical Relationships · Basic Electrical & Mechanical Systems

DOST-SEI Student HubFree 120-item Diagnostic