# Mrs. Wilson's Science 8 Fall Semester Exam - simple machines and science project

## 68 terms

### Precision

How close a group of measurements are to each other

### Accuracy

How close a measurement is to the true or accepted value

### estimate

When you esitmate one place value past the smallest division on the ruler

### decimals

all measurements have these

### units

all measurements have this (except MA)

### SI Units

the system of units that ALL scientists use internationally

### motion

when the distance from another object is changing

### reference point

a stationary object used to determine if an object is moving

### meter

the base SI unit for distance

### speed

is a rate, something calculated per unit of time.

### average speed

the total distance travelled in a set amount of time

### instantaneous speed

the speed at a given moment

### velocity

speed in a given direction

### slope

rise over run on a graph

### acceleration

the rate at which velocity changes

### force

a push or pull in a given direction

### Newton

a unit of force or weight

### net force

the total force on a given object

### unbalanced force

acts on an object resulting in a net force greater than zero, and this will cause it to move in the direction of the greater force

### friction

a force that opposes motion

### static friction

a force of friction between two surface that are not moving

### sliding friction

a force of friction between two solid surfaces sliding past each other

### rolling friction

a force of friction when an object rolls across another object

### fluid friction

a force of friction when a solid object moves though a fluid (gas or liquid)

### gravity

a force that pulls all objects in the universe together

### mass

how much matter is in an object

### weight

the force of gravity pulling an down on an object on the surface of a planet

### free fall

when gravity is the only force acting on an object, it will accelerate as it falls

### air resistance

fluid friction due to an object falling through the air

### terminal velocity

When the force of air resistance is equal to the force of gravity then the object will stop accelerating, and remain at the same speed

### inertia

the resistance of an object to move

### Newton's First Law of Motion

An object in motion will stay in motion, and an object at rest will stay at rest, until an unbalanced force acts on it

### Newton's Second Law of Motion

acceleration depends on the object's mass and on the net force acting on the object.

### Newton's Third Law of Motion

if one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.

### Momentum can be determined by

multiplying the object's mass and velocity

### Law of Conservation of Momentum

The amount of momentum objects have is conserved when they collide. Momentum may be transferred from one object to another, but none is lost.

### work

Work is done on an object when the object moves in the same direction in which the force is exerted.

### one Joule is equal to

exerting a force of 1 N over a distance of 1 m.

### power

Power is the amount of work done on an object in a unit of time.

### machine

it is a device that can make your work easier, not less.

### effort force

the force you exert on a machine

### resistance force

the force the machine exerts on the load. (This is equal to the weight of the load).

### input work

the work you put into a machine

### output work

the work the machine does moving the load

the number of times a machine increases a force exerted on it.

### efficiency

a comparison of the output work to the input work

### inclined plane

a machine where the machine lifts the load as you push horizontally

### wedge

two inclined planes back to back that are used to slice into objects

### screw

an inclined plane wrapped around a cylinder

### lever

a rod that pivots on a fulcrum

### fulcrum

a fixed point where a lever pivots

### wheel and axle

A simple machine that consists of two attached circular or cylindrical objects that rotate about a common axis, each one with a different radius.

### pulley

A simple machine that consists of a grooved wheel with a rope or cable wrapped around it.

### compound machine

A device that combines two or more simple machines.

### problem

The question that you are trying to answer in a project

### hypothesis

A possible explanation for a set of observations or answer to a scientific question; must be testable.

### null hypothesis

the hypothesis where you predict there will not be a relationship between the independent and dependent variables

### alternative hypothesis

the hypothesis where you predict there will be a relationship between the independent and dependent variables

### materials

a list of all of the items used in your project

### procedure

a detailed list of the steps you followed; detailed enough that someone else could use them to do your exact project

### graph

a visual representation of your data

### data table

an area where you record your data in an organized fashion

### results

graph and data table

### conclusion

based on your data, the relationship between the independent and dependent variables

### abstract

a short summary of your entire project

### bibliography

list of sources that provided you with information

### acknowledgements

thanking anyone who helped you