Simple Machines (B) SciOly

What units should answers use unless requested otherwise?

Metric units with significant figures. Metric units make formulas consistent and universal.

What is static equilibrium?

Net force = 0 and net torque = 0. Object stays at rest because all forces and torques balance.

State Newton’s first law relevant to equilibrium.

If no net force, no acceleration. In equilibrium, ΣF = 0 so the object doesn’t move.

Define Mechanical Advantage (MA).

MA = F_out / F_in. Tells how much a machine multiplies effort force; physical meaning: ratio of output to input force.

Define Ideal Mechanical Advantage (IMA).

IMA = D_effort / D_load. Assumes no friction; based on distances, showing how geometry reduces effort.

Define Actual Mechanical Advantage (AMA).

AMA = F_load / F_effort. Includes friction; real-world measurement of force multiplication.

How do you calculate percent efficiency?

Efficiency% = (AMA / IMA) × 100%. Shows how much input energy actually does useful work.

IMA of an inclined plane formula.

IMA = slope length / vertical height. Longer slope spreads lifting force over distance.

IMA of a wheel & axle formula.

IMA = R_wheel / R_axle. Larger wheel relative to axle reduces required effort.

IMA of a pulley system.

IMA ≈ number of supporting ropes. Each rope shares part of the load; total effort decreases.

IMA of a screw (approx).

IMA ≈ 2πR / pitch. More turns = less force per turn; converts rotational motion into linear force.

IMA of a lever.

IMA = effort arm / load arm. Longer effort arm allows smaller force to lift a load; distance tradeoff.

What is the relationship between work in an ideal machine?

Input work = output work (Fin·din = Fout·dout). No energy is lost; force and distance trade off.

Formula for gravitational potential energy.

PE = mgh. Work done to lift a mass; shows energy stored by position.

Formula for kinetic energy.

KE = 1/2 m v^2. Energy due to motion; used when objects move in the machine.

Define coefficient of friction µ.

µ = F_friction / N. Shows how surface interaction resists motion; reduces AMA relative to IMA.

What does AMA < IMA indicate?

Friction or deformation is present; efficiency < 100%. Some input energy is “lost” to non-useful work.

Name the six simple machines.

Lever, Wheel & Axle, Pulley, Inclined Plane, Wedge, Screw. Each multiplies force or changes direction.

Order in a first-class lever.

Effort — Fulcrum — Load. Pivot between effort and load; MA can be >1 or

Order in a second-class lever.

Fulcrum — Load — Effort. Effort farther from pivot than load; always MA > 1.

Order in a third-class lever.

Fulcrum — Effort — Load. Effort closer to pivot; MA < 1 but load moves farther.

Why does a ramp reduce force needed?

Longer distance spreads the lifting; work remains the same. Formula: IMA = slope length / height.

Why does a pulley with multiple ropes reduce effort?

Load shared among ropes; effort per rope decreases. IMA ≈ number of supporting ropes.

Why is AMA lower than IMA?

Friction/resistance reduces output force; some input energy lost as heat or deformation.

Why does a second-class lever always have MA > 1?

Load is between fulcrum and effort; effort arm longer than load arm.

Why does a third-class lever have MA < 1?

Effort is between fulcrum and load; need more force but load moves farther.

When do potential & kinetic energy appear on a problem?

Lifting = PE; moving parts = KE; conservation of energy may apply.

What does conservation of energy mean for ideal machines?

Input energy = output energy; force × distance trade-off.

What extra physics topics may appear?

Newton’s laws, inertia, momentum, acceleration, conservation of momentum; for reasoning in machines.

Units & sig figs — what to remember.

Always include metric units, round appropriately; ensures correct numeric answers.

How do you count supporting rope segments in a pulley?

Count only segments supporting the load; free ends not counted.

How do you compute MA for compound machines?

Multiply MAs of each stage; efficiency = product of stage efficiencies.

What is required for the build/test device?

A calibrated lever-based measuring device; must be rigid, accurate, repeatable.

Build/test calibration steps (short).

Use known masses to calibrate, adjust pivot, record data; ensures correct torque measurements.

Key practical tips for lever device construction.

Rigid base, low-friction pivot, clear measurement marks, secure arms; prevents error.

Quick friction test for a device.

Compare AMA to IMA; large difference = high friction; fix pivot/contact.

One-minute study routine.

Review 3 formulas, solve 2 problems, fix mistakes; reinforces understanding quickly.

Why is IMA of a lever equal to effort arm / load arm?

Longer effort arm multiplies force; torque = F × distance, so same torque requires smaller force.

Why does a wedge multiply force?

Wedge converts force in one direction into force along the slope; splits or lifts material with less effort.

Why does a screw multiply force?

Rotational motion converted into linear motion; more turns = less effort per turn.

Why does a wheel & axle multiply force?

Larger wheel radius moves farther than axle; smaller effort applied over longer distance moves load.