Chapter 7 Work & Simple Machines Flashcards
Mechanical work (W)
when a force acts on an object to move it parallel to the force vector.
Formula for mechanical work
W = F x d (Work in joules is Force in newtons x displacement in meters)
Work is what type of quantity? (scalar or vector?)
scalar (it can be positive, negative, or zero)
A book has what kind of energy after it is raised?
gravitational potential energy
A larger motor delivers more ___ to move the vehicle than a smaller motor.
force
Power (P) is the rate of doing ___?
work
Formula to computer mechanical power
P = Work / change in time (time interval)
Watt (W)
the unit of power in the SI
One watt is 1 J of work done in 1 s
Simple machines
tools, composed of basic mechanical parts, that cannot create their own energy
formula for efficiency
efficiency = W out / W in x 100%
What is the “load” or “resistance”?
the system to be moved (by a machine)
The force you exert on the simple machine
The effort force [ F(e)]
The force that the load exerts on the machine
the resistance force [ F(r)]
Lever
a rigid bar that rests on a pivot point called a fulcrum (like your Revolution board)
Torque
the product of a force and the distance from the pivot point.
Law of Torques
formula that applies to lever systems in rotational equilibrium (w(1) x l(1) = w(2) x l(2)
Three types of levers
1st Class (with the fulcrum between the resistance and effort points like a seesaw), 2nd Class (with the fulcrum at one end and effort at the other like wheelbarrow), and 3rd Class (fulcrum at one end and resistance at the other end like arm/hand).
When a lever doesn’t have equilibrium, what occurs?
acceleration and motion
Rotational motion
movement of an object about a central axis or pivot point
a wheel
any rotating object that has a force applied to it at some distance from the center axis (creating torque).
gear
a modified wheel and axle with “teeth” around its circumference that mesh with another gear
two types of gears
effort gear and resistance gear
