SCI 101 Chapter 2 - Motion

3 important combinations of length and time

1. Speed 2. Velocity 3. Acceleration

Three Types of Motion

1. Vertical Motion 2. Horizontal Motion 3. Combination of 1 and 2

Negative Acceleration

(a.k.a deceleration) slowing down or coming to a complete stop

momentum

(p) the product of the mass (m) of an object and its velocity (v) - momentum = mass x velocity

Newton's 1st Law of Motion

- "the law of inertia" - every object remains its state of rest or its state of uniform straight-line motion unless acted upon by an unbalanced force - inertia resists any changes in motion

Electromagnetic Force

- Acts between electrically charged parts of an atom - is responsible for most of the reactions in chemical reactions

Velocity

- Describes speed (How fast is it going?) and direction (Where is it going?) - graphical representation of vectors: length=magnitude; arrowheads=direction

Constant in Newton's Equation of Gravity

- G - 6.67 x 10 ^ -11 N m squared/kg squared

Weak Nuclear Force

- Involved in certain nuclear reactions - governs the decay of radioactive nuclei

Impulse

- a force acting on an object for some time t - produces a change in momentum - impulse = Ft

Speed

- a measure of how fast you are moving - distance per unit of time

Force

- a push or a pull capable of changing an object's state of motion - overall effect determined by the (vector) sum of all forces - the "net force" on the object

Galileo and Newton

- all objects fall at the same rate - no force required for uniform horizontal motion - reasoning based upon measurements

Friction

- always acts in a direction opposite motion - is a force - must be balanced if an object moves at a constant velocity

Centrifugal force

- apparent outward tug as direction changes

Newton's Law of Gravitation

- attractive force between all masses - proportional to product of the masses - inversely proportional to separation distance squared - provides centripetal force for orbital motion

Speed

- change in position with respect to time - average speed - most common measurement - instantaneous speed - time interval approaches zero - speed = distance/time (v=d/t)

Three Laws of Motion

- first detailed by Newton (1564-1642 AD) - concurrently developed calculus and a law of gravitation - published Principia - essential idea: forces

Newton's 2nd Law of Motion

- forces cause accelerations - units = Newtons (N) - proportionality constant = mass - more force, more accleration - more mass, less accleration

symbol for acceleration due to gravity

- g - is a constant acceleration - is about 9.8m/seconds squared on Earth - slows objects that are thrown upward

Four Fundamental Forces

- gravitational - electromagnetic - weak nuclear force - strong nuclear force They cannot be explained in the terms of other forces!

Aristotle

- heavier objects fall faster - objects moving horizontally require continuously applied force - relied on thinking alone

Horizontal Projectile

- horizontal velocity remains the same (neglecting air resistance) - taken with vertical motion = curved path

Momentum

- important property closely related to Newton's 2nd law - includes effects of both motion (velocity) and inertia (mass) - p = mv

Strong Nuclear Force

- involved in holding the nucleus together - stronger than electromagnetic and gravitational force

Constant Speed

- moving over equal distances in equal periods of time - neither speeding up nor slowing down

Acceleration

- rate at which motion changes over time - speed can change - direction can change - both speed and direction can change - acceleration = change in velocity/time elapsed = 🔼v/t

Vertical Projectile

- slows going up - stops at top - accelerates downward - force of gravity acts downward throughout

Newton's 3rd Law of Motion

- source of force: other objects - 3rd law: relates force between objects - "Whenever two objects interact, the force exerted on one object is equal in size and opposite in direction to the force exerted on the other object."

Inertia

- the behavior of matter to persist in its state of motion - the tendency of an object to remain in unchanging motion whether actually moving or at rest, when the net force is zero

weight

- the force of gravity acting on a mass - a force - in metric units is measured in newtons (N) - is found my w = mg

Net force

- the sum of all the forces acting on an object - "final", after the forces are added

Free Fall

- when objects fall toward Earth without considering air resistance - considers only gravity and neglects air resistance - object should cover distance proportional to the square of the time of the fall - velocity increases at a constant rate

Newton

1 kg m/s squared

2 Aspects of Motion

1) a change of position 2) the passage of time

3 Ways Motion can Change

1) by changing the speed 2) by changing the direction of travel 3) by changing both the speed and the direction of travel

Circular Motion

Accelerated motion (direction changing)

Gravitational Force

Acts between all objects

Projectile Motion

An object thrown into the air

centripetal force

F = m v squared/r - measure in N or kg s/s

Free Fall

Falling under influence of gravity without air resistance

Weight

Force of gravity acting on the mass

Inertia

Measure of an object's tendency to resist changes in its motion (including rest)

Mass

Quantitative measure of inertia; the amount of matter - measured in kilograms

Measuring motion

Two fundamental components: - change in position - change in time

Acceleration

a change of velocity per unit time

Newton's Law of Inertia

a moving body maintains a constant velocity unless a force acts on it

Force

a push or pull that is capable of changing the state of motion of an object

centripetal acceleration

ac = v squared/r - measured in m/s squared

Velocity

describes the speed and direction of a moving object - m/s

Newton's First Law of Motion

every object retains its state of rest or its state of uniform straight-line motion unless acted upon by an unbalanced force

Radius

measured in m

Newton's Second Law of Motion

the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to the mass of the object

Motion

the act or process of changing position relative to some reference during a period of time

Newton's Law of Gravitation

the idea that a force exists between two bodies and depends on the product of their masses and the square of the distance between them

impulse

the product of the force and the time of application - impulse = Ft

mass

the property that determines how much an object resists a change in motion

Law of Conservation of Momentum

the total momentum of a group of interacting objects remains the same in the absence of external forces

Newton's Third Law of Motion

whenever two objects interact, the force exerted on one object is equal in strength and opposite in direction to the force exerted on the other object