PLTW Simple Machines

What are simple machines?

Mechanisms that manipulate magnitude of force and distance

What are the six simple machines?

Lever, wheel and axle, pulley, inclined plane, wedge, screw

What is mechanical advantage?

The ratio of the magnitude of the resistance and effort forces. The ratio of distance traveled by the effort and the resistance force.

What is work?

The force applied on an object times distance the object ravels parallel to the force

If the MA is greater than 1:

there is LESS EFFORT FORCE but GREATER EFFORT DISTANCE to overcome the resistance force.

If the MA is less than 1:

there is GREATER EFFORT FORCE but LESS EFFORT DISTANCE to overcome the resistance force.

What is IMA?

ideal mechanical advantage and it is the ratio of distance traveled by effort and resistance

What is AMA?

actual mechanical advantage and it is the ratio of force magnitudes

What is a lever?

A rigid bar used to exert a pressure or sustain a weight at one point of its length by the application of a force at a second point and turning on a fulcrum at a third

What is a first class lever?

The fulcrum is located between the effort and the resistance

What is a second class lever?

resistance is located between the fulcrum and the effort force

ERF

mechanical advantage is always greater than one

What is a third class lever?

The effort is located the middle of the resistance and the fulcrum

REF

mechanical advantage is always less than one

What is moment?

The turning effect of a force about a point equal to the magnitude of the force times the perpendicular distance from the point to the line of action from the point to the line of action from the force

Formula for moment

M= d x F

What is torque?

A force that produces or tends to produce rotation or torsion

What is rotational equilibrium?

When all the moments are equal and balanced

What is efficiency?

The percentage of work input that is converted to work output

Formula for efficiency?

(AMA/IMA)100

Formula for wheel and axle IMA?

Diameter of effort (wheel or axle)/ diameter of resistance (wheel or axle)

What is a pulley?

A pulley is a lever consisting of a wheel with a groove in its rim that is used to change the direction and magnitude of a force exerted by a rope or cable

What is a fixed pulley?

First class lever with IMA of 1 and changes direction of force

What is a movable pulley?

A second class lever with an IMA of 2 and the force directions stay the same

What is a pulley's IMA?

number of strands opposing the force of the load (not including the very first strand in the system of movable pulley)

How do you calculate the IMA of a compound machine?

The mechanical advantages multiply

What is an inclined plane?

A flat surface set at an angle or incline with no moving parts

What is the resistance of an inclined plane?

The height

What is a wedge?

Functions as an inclined plane but tapers to a thin edge and is used for splitting, raising heavy bodies, or for tightening by being driven into something

What are the two components of a screw?

An inclined plane wrapped around a cylinder forming the path and pitch and a wheel and axle used to create rotary motion.

What is effort arm distance?

the length of the wrench

What is Pitch?

distance between threads and linear distance traveled by 1 rotation of the screw

What is 1/2 in [1/2 13 NC]?

the diameter

What is 13 in [1/2 13 NC]?

threads per pitch

What is NC in [1/2 13 NC]?

thread description coarse or fine

If 21 threads per inch, than what is pitch of an inch?

pitch is 1/21 of an inch