Quiz 6 2017- Force, Work and Energy Study Guide
6th Grade Science – Miss Fox
Force: a push or pull exerted on an object in order to change the motion or direction of an object.
Newton (N): units used to measure force.
Calculating Force: F = M x A (Force = Mass multiplied by Acceleration)
Friction: force that opposes motion between surfaces. There are four types of friction:
How to decrease friction: add wheels or rollers, lubricate the surface (oil), make the surface smoother, remove weight or pressure.
How to increase friction: make the surface rougher or bumpier, add weight or pressure.
Work: is the transfer of energy to an object by using a force that causes the object to move in the direction of the force.
Joule (J): is the unit used to express energy.
Calculating Work: W = F x D (work = force multiplied by distance)
Energy: is the capacity to do work.
Potential - is stored energy waiting to happen.(for example) a book sitting on a shelf.
Kinetic - energy in motion or happening now.(for example) a book falling off a shelf.
Energy Conversion - Energy can be transferred from potential to kinetic and between objects.
Law of conservation of energy: the law that states that energy cannot be created or destroyed but can be changed from one form to another. When energy is transferred from one type to another the total energy stays the same.
Machine: a device that helps do work by either overcoming a force or changing the direction of the applied force.
Simple machines (Simple Six): make work easier for us by allowing us to push or pull over increased distances.
· A lever consists of a bar that pivots at a fixed point called a fulcrum (stapler, clothespin, pencil).
To decrease the effort and make our work easier, we can move the fulcrum closer to the load/resistance. Moving the fulcrum further away from the load and closer to the effort makes our work harder and requires more effort force to move the load.
· Wheel and axle two circular objects of different sizes; the wheel is the larger of the two circular objects (clock, doorknob).
· A pulley consists of a wheel over which a rope, chain, or wire passes (flag pole, mini blinds).
· Inclined plane is a straight surface, which facilitates the raising of loads; a ramp (staircase, ladder, ramp).
· Wedge is made up of two inclined planes and moves; often used for cutting (scissors, door stop).
· Screw consists of an inclined plane wrapped around a cylinder (lightbulb, jar with lid).
Compound machines: are machines made of more than one simple machine (sail boat, car, wheel barrow).
Mechanical Advantage: a number that tells how many times a machine multiples force.
Work Input: is work done on a machine. Work Output: is work done by a machine.
Mechanical advantage (MA) = output force
input force
Mechanical Efficiency: the less work a machine has to do to overcome friction, the more efficient the machine is.