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position
area occupied by an object
displacement
The direction and length of a straight line from the starting point (reference point) to the ending point of an object's motion (units= meters, direction), it is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.
constant speed
this means that average speed = instantaneous speed because the speed is the same every instant (units= m/s)
average speed
total distance covered over total time (units = m/s)
acceleration
rate at which velocity changes (how fast velocity changes), either speed, direction, or both.
change in velocity (m/s) / change in time (s) = (m/s², direction)
a = ∆v / ∆t = (v final - v initial) / (t final - t initial),
(units=m/s², direction)
deceleration
negative acceleration, decrease in velocity, slowing down (m/s², direction)
reference point
point that appears to stay in place (starting point), it is a non-moving object with which to compare movement of another object
average velocity
displacement over total time (m/s, direction)
s = d/t , d = s x t , t = d/s (m/s)
speed equations
instantaneous speed
speed that something has at any one instant (m/s)
m/s²
units for acceleration= meters per square seconds or meters per second squared
average acceleration
final speed minus initial speed over time, (vf - vi)/ time (m/s²)
speed
the rate at which an object moves
distance (m) / time (s) = (m/s)
s = d / t
velocity
the rate at which an object's displacement changes
displacement (m) / time (s)
s = ∆x/∆ t, describes speed and direction of motion (m/s, direction)
resultant velocity
the sum of the velocity vectors, for example velocity forward added to velocity backwards (m/s, direction)
positive acceleration
positive acceleration, increase in velocity, speeding up (m/s², direction)
instantaneous velocity
v = v₀ + (a x t), initial velocity (might be zero) added to the acceleration times the time. (m/s, direction)
distance
how far an object moves from the reference point (m), it is a scalar quantity that refers to "how much ground an object has covered" during its motion.
scalar
have magnitude (size) only, such as distance and speed
vector
have both magnitude (size) and direction, such as displacement, velocity, and acceleration
qualitative measurement
a measurement that can be observed but not measured numerically.
quantitative measurement
refers to a type of information based in quantities or measured numerically (with numbers).
accuracy
the degree of closeness of measurements of a quantity to that quantity's actual (true) value.
precision
also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.
inertia
the resistance of any physical object to any change in its motion (including a change in direction). In other words, it is the tendency of objects to keep moving in a straight line at constant linear velocity, or to keep still. It is directly related to mass. It increases with more mass, it decreases with less mass.
mass
a property of a physical body, giving rise to the phenomena of the body's resistance to being accelerated by a force. Instruments such as balances or scales use those phenomena to measure it. The SI unit of it is the kilogram (kg).
Newton's 1st Law
An object will remain at rest or keep moving with a constant velocity unless an unbalanced force acts on it. Note: Velocity is a vector quantity which expresses both the object's speed and the direction of its motion; therefore, the statement that the object's velocity is constant is a statement that both its speed and the direction of its motion are constant. Consequently,
1) An object that is at rest will stay at rest unless an external force acts upon it.
2) An object that is in motion will not change its velocity (speed or direction) unless an external force acts upon it.
motion
movement from a reference point.
weight
It is a measure of the force of gravity acting on an object's mass.
mass (kg) x gravitational acceleration (m/s²) = force (newtons)
Weight= Fg = m • ag, where ag is gravitational acceleration (9.81 m/s²)
Note: weight depends on the gravitational acceleration where mass is independent, i.e. mass is the same anywhere while weight changes when gravity changes.
Newton's 2nd Law
acceleration is calculated by dividing the force exerted on an object by the mass of the object." [ a (m/s2) = F (N) / m (kg), also known as F (N) = m (kg) • a (m/s2) ]
= mass (kg) x acceleration (m/s2) OR F = m • a
direct proportionality
It is when one variable changes at the same rate of another variable, such as Force and acceleration in F = m • a.
indirect proportionality
(also known as inversely proportional) It is when a variable changes at the reciprocal rate of another variable, such as speed and time in s = d / t. When one increases, the other decreases.
force
Physical push or pull
mass (kg) x acceleration (m/s²) = (newtons)
F = m • a
net force
It is the vector sum of all the forces that act upon an object.
equilibrium
The net force must be zero (balanced forces).
static equilibrium
An object is at rest with a constant velocity of zero. Ex: a book resting on a table has weight pushing down on the table and the normal force of the table pushing up on the book.
dynamic equilibrium
An object is moving with constant velocity because the speed and direction are NOT changing. Ex: a car (or other vehicle) travelling with no acceleration, moving in a straight line (no change in direction) at constant speed
Force due to gravity (gravitational force)
same as weight!
It is a measure of the force of gravity acting on an object's mass.
mass (kg) x gravitational acceleration (m/s²) = force (newtons)
Weight= Fg = m • ag, where ag is gravitational acceleration (9.81 m/s²)
Note: weight depends on the gravitational acceleration where mass is independent, i.e. mass is the same anywhere while weight changes when gravity changes.
Normal Force
It is the support force exerted upon an object that is in contact with another stable object. It is produced by a surface pushing back. Ex: When a book rests on a table, the table provides a normal force pushing back on the book.
tension force
It is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends.
friction force
It is the force exerted by a surface as an object moves across it or makes an effort to move across it.
Friction: What causes friction?
It results from the two surfaces being pressed together closely, causing intermolecular attractive forces between molecules of different surfaces. As such, it depends upon the nature of the two surfaces and upon the degree to which they are pressed together.
Friction: static friction
It results when the surfaces of two objects are at rest relative to one another and a force exists on one of the objects to set it into motion relative to the other object. Ex. push on a heavy box, but not hard enough to move it.
Friction: kinetic friction
It results when an object slides across a surface. Ex. while pushing a box across a floor, the floor surface offers resistance to the movement of the box.
Friction: coefficient of friction
coefficient value is dependent primarily upon the nature of the surfaces that are in contact with each other. (no units) equation: μ = Ffrict/Fnorm
Friction: Two materials with high coefficient of friction?
rubber on pavement (generally rougher surface)
Friction: Two materials with low coefficient of friction?
ice on steel (generally smoother surface)
Newton's 3rd Law
In every interaction, there is a pair of forces acting on the two interacting objects. The size of the force on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs. Ex: a normal force produced by a surface when a force pushes on it.
Conserved quantity
The quantity or total amount is constant, none is lost and none is gained. Quantities are usually not truly conserved because isolated systems do not exist in the real world.
Newton's law of conservation of energy
Energy can neither be created nor destroyed, it can only be transferred
