science 8: mechanical efficiency

force

a push or a pull that acts on an object

what are the different types of forces?

contact and non-contact forces

what can a force change?

change in speed, direction, size or shape, strength

mass

amount of matter in an object

weight

amount of force on an object due to gravity, measured in kg

what are the 6 simple machines?

pulley, lever, wheel and axel, inclined plane, screw, wedge

what is the formula for the force of gravity?

Fg=mg

what is an inclined plane?

a flat surface tilted on an angle

what is a lever?

a bar that pivots on a fixed support

what is a wedge?

a piece of material that is thick on one end and thin on the other

what is a screw?

an inclined plane wrapped around a cylinder/wedge

what is a pulley?

a rope or chain wrapped around a wheel

what is a wheel and axle?

a wheel with a rod attached in the middle

what are the three parts of a lever?

force/effect, load/resistance, fulcrum

what is the gravitational constant?

9.8N/kg

what is a first class lever?

fulcrum between effort and load, changes direction of the force

what is a second class lever?

load between fulcrum and effort, changes strength of the force

what is a third class lever?

effort between fulcrum and load, force is applied in the direction you want to move the load, transfers the force

what are the two forces that are involved when machines do work?

input and output forces

mechanical advantage

the ratio of the output force to the input force

what is force measured in?

newtons (N)

what is the formula for MA?

output force/input force

what are three ways simple machines change the force applied to them?

increase the force, transfer the force, change the direction of the force

what happens if the MA>1?

changes strength of force, 2nd class lever

what happens if the MA<1?

get more distance and less force, 3rd class lever

what happens if the MA=1?

changes direction of force, 1st class lever

what is the formula for MA in a lever?

MA=effort arm length/load arm length

what is the formula for MA in an inclined plane?

MA=distance of effort/distance of resistance

what is the formula for MA in a pulley?

count the number of ropes that support the movable load