Galileo: First Modern Scientist

Telescopic Discoveries: Rings of Saturn

Galilean Satellites

Phases of Venus

Craters an Moon

Milky way consists of stars

Sunspots

Laws of Motion

2) Projectile (ballistic) motion: vertical component dependent only on gravity; horizontal component independent of vertical,.

Tycho

Danish astronomer - mid 1500's

Very complete and accurate measurements of positions' of planets and stars

No telescopes yet; used instruments like large protractors

1) Took several measurements and averaged data

2) Measured planetary positions at many positions in orbit

3) Compensated for atmospheric refraction and sag in instrument

Kepler used his data for his laws.

Newton's Laws of Motion

1) An object in motion will remain in m6tion with the same velocity unless acted upon by an external force; an object at rest will remain at rest unless acted upon by an external force.

2) A=F/M

For same mass greater force - greater acceleration.

For same force greater mass - smaller acceleration.

3) If object A exerts a force on object B, object B will exert an equal but oppositely directed force on object A. (Action - Reaction)

MVR=Constant

For same m,

R smaller - V greater

R larger - V smaller

Kepler's 2nd Law: Planet moves faster @ perihelion (R smaller) than @ aphelion.

g ~ 1/r²

g decreases rapidly with distance

Gravity pulls harder on the part of an object that is closer.

.-. gravity tries to stretch it.

Ex: (Long) space ship is orbit.

Contents of ship weightless only when at center of mass of ship

Ocean Tides

Moon's gravity pulls harder an part of earth closest to it. Causes oceans to bulge on sides nearest and opposite.