2ND QUARTER GENPHY QE

force

• referred to as the pull or push exerted upon an object as it interacts with another object

• has magnitude and direction

• Newton (N)

contact force

direct physical contact

• normal

• friction

• tension

non contact force

action-at-a-distance forces

• magnetic

• electric

• gravitational

normal force

exerted by a surface on an object, perpendicular to the surface

friction force

force exerted by a surface on an object, parallel to it

tension force

pulling force exerted by a cord on an object

magnetic force

attraction or repulsion between moving charged particles surface

electric force

force exerted by one electric

force

change on another

garvitational force

force of attraction between two objects with mass

free body diagram

diagram showing the relative magnitude and direction of all forces acting upon an object in a give situation

steps for drawing FBD

1. identify the object

2. identify all forces acting on ot and their direction

3. draw arrows proportional to force magnitude

4. label each arrow

newton’s first law

“an object at rest, remains at rest and an object in motion remains in motion at constant speed in a straight line unless acted on by an unbalanced force”

• law of interia 

inertial frame of reference

• frame of reference at rest or moving with constant velocity in a straight line

law of acceleration

“the acceleration of a moving object depends upon its mass and the force acting on it”

• F=ma

• Heavier objects require more force to accelerate

• lighter objects require less force to accelerate

limitations of 2nd law

• applies only to external forces

• object’s mass must be constant

• valid only in inertial reference frames

law of interaction

“for every action, there is an equal and opposite reaction.”

• Fa = - Fr

acceleration

change in velocity.

• when the net external force is not zero, acceleration occurs

action reaction pairs

• forces always come in pair of equal magnitude and opposite direction, acting on different objects.

• never act on the same object

rotational motion

• motion of an object around a central axis or point. every point on the object moves in a circle

linear motion

• movement of an object from one place to another in a straight line

moment of inertia

• rotational equivalent of mass

mass

• greater the mass of an object, the greater its moment of inertia

mass distribution

farther the mass is distributed from the axis of rotation, greater the moment of inerta

torque

rotational force that tends to cause an object to rotate

• force

  • the larger the force, greater the torque

• lever arm

• angle

net torque

in a system is the sum of the torques on all the particles in the system

if tnet ≠ 0, then the system will spin

gravity

• weakest of the four fundamental forces of the universe

distance

• inversely proportional to the square of the distance between 2 objects

mass

• gravitational force between 2 object increases (directly proportional) as the mass of their object increases

newton’s law of gravitation

• every 2 masses attract each other with a force proportional to their masses and inversely proportional to the square of the distance between them.

kepler’s contribution

formulate three laws of planetary motion based on tycho braahe’s observation

copernicus heliocentric theory

simpler explanation of planetary motions than the geocentric theory

tycho brahe’s observation

revealed flaws in copernicus’s theory through accurate measurements

1st law of planetary motion

• orbits of all planets are elliptical, and the sun is located at one of the foci of these elliptical orbits

• planet-to-sun distance is constantly changing as the planet goes around its orbit

• sun’s center is always located at one focus of the orbital ellipse

ellipse

each planet’s orbit about the sun

2nd law of planetary motion

• every planet sweeps an area at a constant rate

• planets dont move with constant speed; their speed vaies, so the line sweeps out equal parts of an area in equal times

• planet moves fastest at perhelion and slowest at aphelion

perhelion

planet’s closest approach to the sun

aphelion

farthest separation

3rd law of planetary motion

• square of the planet’s period is proportional to the cube of the planet’s mean distance from the sun