Efficient Simple and Compound Machines - Video Notes

A set of question-and-answer flashcards covering the key concepts from the notes on simple machines, mechanical advantage, efficiency, and compound machines.

What does Mechanical Advantage (MA) represent?

The number that tells us how much a machine multiplies your effort or makes a job easier.

What does MA > 1 indicate? MA < 1?

MA > 1 means the machine multiplies force (easier to lift/move); MA < 1 means it increases speed or distance.

Define Efficiency in machines.

The percentage of work input that becomes work output; always less than 100% due to friction.

What are the general functions of a simple machine?

Transferring a force, changing the direction of a force, increasing the magnitude of a force, or increasing the distance or speed of a force.

Define a lever.

A rigid bar that rotates about a fixed point called the fulcrum.

Name and describe the three classes of levers.

First-class lever: fulcrum between effort and load; Second-class lever: load between fulcrum and effort; Third-class lever: effort between fulcrum and load.

What is a First-Class Lever used for?

It can change the direction of the force and, depending on arm lengths, can multiply force or magnify speed/distance.

What characterizes a Second-Class Lever?

The load is between the fulcrum and the effort; it multiplies force (MA > 1).

What characterizes a Third-Class Lever?

The effort is between the fulcrum and the load; it does not increase force and MA is typically < 1, magnifying speed/distance.

What are the major parts of a lever?

Effort (input force), load (output force), fulcrum, effort arm, load arm.

If a crowbar has an effort arm of 0.75 m and a load arm of 0.25 m, what is the mechanical advantage?

MA = 0.75 / 0.25 = 3.

Define an inclined plane.

A flat surface that is higher on one end; reduces the force required by applying the force over a longer distance.

What is the main purpose of an inclined plane?

To make it easier to move objects up by spreading the work over a longer distance.

Define a wedge.

A simple machine made of two inclined planes back-to-back; used to split, cut, or push apart.

Define a screw.

An inclined plane wrapped around a cylinder; used for drilling and converting rotational motion to linear motion; pitch affects mechanical advantage.

Define a wheel and axle.

A wheel attached to an axle; rotating wheel causes the axle to turn; a larger wheel relative to the axle provides mechanical advantage; applying force to the wheel vs the axle has different effects on force vs speed.

What is the role of a fixed pulley?

Changes the direction of the force but does not provide a mechanical advantage.

What is the role of a movable pulley?

Provides a mechanical advantage equal to the number of supporting ropes.

What is a compound pulley?

A pulley arrangement that reduces the effort to lift the load to less than half the weight, though it travels a longer distance.

What is a compound machine?

Two or more simple machines working together to make work easier.

Give an example of a compound machine.

Scissors (two wedges and two levers); wheelbarrow; pencil sharpener; crane.

What is the effect of combining two simple machines on mechanical advantage?

Total mechanical advantage increases; less effort is needed, but the task may require longer movement.

How does ramp length relate to mechanical advantage?

A longer ramp increases mechanical advantage.

How do lever arm lengths affect a lever’s function?

If the effort arm is longer than the load arm, the lever acts as a force multiplier; if the load arm is longer, it acts as a speed multiplier.

What is the relationship between the wheel’s radius and mechanical advantage in the wheel and axle?

The wheel’s radius acts as the lever’s effort arm; a longer radius (larger wheel) increases the mechanical advantage.

What is the key takeaway about simple vs. compound machines?

Simple machines multiply force or change direction to make work easier; compounds combine simple machines to increase overall efficiency and mechanical advantage.