# Poem - Motion, Forces, and Simple Machines

### 34 terms by moonpoem

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### meter

SI unit of distance, equal to approximately 39.37 inches

### m

abbreviation for meter

S=d/t

### speed units

distance unit divided by a time unit, such as meters per second or m/s

### instantaneous speed

speed of an object at any instant of time

### speedometer

gives the instantaneous speed when you are riding in a car

### average speed

Total distance divided by total time; s=d/t

### constant speed

This happens when an object's speed doesn't change for a period of time

d=st

### velocity

the speed of an object in a particular direction

### motion

a state of change

### acceleration

the rate at which velocity changes over time

### acceleration equation

(final speed - initial speed) / time

### gravity

attractive force any two objects that depends on the masses of the objects and the distance between them

### Newton's Law

1. an object at rest willl stay at rest, and an object in motion will stay in motion at constant velocity unless acted upon by an unbalanced force 2. force = massXacceleration 3. for every action there is an equal and opposite reaction

### force

acted upon an object to change an object's speed, direction, or both

### balanced forces

2 or more forces exerted on an object that cancel each other out and don't cause a change in motion

### unbalanced forces

2 or more forces that effects don't cancel each other out and cause a change in motion

### net force

the combination of all forces acting on an object

### Newton's First Law

a moving object moves in a straight line with constant speed unless an unbalanced force acts on it

### friction

the force that opposes the motion of one surface as it moves across another surface

### how to keep object moving when friction is acting upon it

you have to keep pushing or pulling on the object to overcome the frictional force

### In what direction is the force of friction exerted?

opposite direction

### size of friction force depends on what?

1. 2 surfaces involved
2. The rougher surfaces are, the greater the friction.

### inertia

the tendency of an object to resist a change in motion

to move and stop

### mass

a measure of how much matter an object is made of.

### Newton's Second Law

if an object is acted upon by a net force, the acceleration of the object will be in the in the direction of the net force, and the acceleration equals the net force divided by the mass.

### acceleration equation - Newton's 2nd Law

acceleration (in m/s2) = net force (in N) / mass (in kg)

### Newton's Third Law

for every action, there is an equal and opposite reaction, or when one object exerts a force on a 2nd object, the 2nd object exerts equal force in the opposite direction on the first object.

### action forces

the force you exert when you push on something

### reaction forces

are equal and opposite forces exerted in response to applied forces

### force equation - Newton's 2nd Law

force=mass x acceleration

### why don't action and reaction forces cancel?

action-reaction forces are equal and opposite, but they act on two different objects

Example: