Astro Guide Unit 3 A linear 3 1 The length of an object is a n measure 3 1 The difference in direction between 1 points as measure from a specified third point is a n 3 2 When a circle is divided into 360 equal parts each part is called a 3 2 How many degrees in a circle A angular measure A degree A 360 A 2 x 10 2 A 3 0 x 10 7 3 3 4 x 10 5 2 x 10 3 powers of 10 notation 3 3 5 1 x 10 4 1 7 x 10 3 powers of 10 notation 3 4 If a building 500 meters away has an angular height of 1 degree how tall is it approximately A 9m convert 1 degree to seconds of arc 1 degree 60 sec of arc min of arc x 60 min of arc degree 3600 sec of arc Small angle eqns Know d and D want use 2 06 x 10 5 x d D Know and D want d use d x D 2 06 x 10 5 Know and d want D use D 2 06 x 10 5 x d 3 4 What is the approximate angular size of a 1cm stick when viewed from 1km A 2 size of the stick and distance of stick must be in the same units to use the small angle eqn 3 4 When Mars is closest to the Earth its angular diameter is about 17 and its distance is about 7 7 x 10 7 km The approximate diameter of Mars is A 6 4 x 10 3 km 3 4 If a is the angular size of an object d is the real size of the object r is the distance to the object than these quantities are related by A a 206265 d r 3 4 Jupiter is about 1 4x10 5 km in diameter and sometimes is a close as 6 3x10 8 km What is Jupiter s approximate angular size when it is closest A 46 3 4 A 2 00 meter tall man is observed to have an angular height of 570 degree 2060 How far away is he A 200m angles must be in seconds of arc 3 5A The number 24 33 has significant figures A 4 the decimal point has no bearing on the sigfigs 3 5A The number 0 7 has significant figures A 1 the leading zero is just to draw attn to the decimal don t count it 3 5B sigfigs 02 cm x 27 cm cm 2 A 5 only 1 sigfig in 02 so can only have answer w 1 sigfig 3 5B sigfigs 3 95 cm x 8 762 cm cm 2 A 34 6 only 3 sigfigs in the answer bc 3 95 only has 3 3 5B Suppose a spaceship is traveling at 9 9km sex In 2 5 seconds it will travel km sigfigs Distance speed x time A 25 bc each answer only has 2 sigfigs 3 9A The model of the solar system has the Earth at the center 3 9A In order to make the model of the solar system fit observations many circles on circles called epicycles were added to fit observations A Ptolemaic A Ptolemaic 3 9B Occam s razor is that idea that the A best theory is the one with the fewest assumptions 3 10 Copernicus explained the retrograde motion of superior planets as due to A The Earth s motion about the Sun The idea that the Sun causes the Earth to revolve about it was introduced to 3 10 modern astronomers by A Kepler 3 10 8 x 10 4 8 x 10 4 A 1x10 8 subtract exponents with negatives add the neg 3 10 1 69 x 10 7 x 1 x 10 2 A 1 69 x 10 5 add exponents 3 10 Brahe found that the planets move in ellipses with the Sun at one focus A Wrong Kepler did this 3 10 Match a description with astronomer Tycho Brahe A 1546 1601 famous for his accurate observations of positions of planets and stars did not use telescope 3 10 Tycho Brahe and Johannes Kepler were early astronomers Kepler studied under Brahe Brahe discovered that the planets move in ellipses A Wrong Kepler discovered the elliptical motion using observations made by Brahe 3 13 The closed orbit that a satellite might have about the Earth is called a n A ellipse if closed must be ellipse or circle circle not offered answer 3 13 A spacecraft is launched from Earth at a speed of 30 km sec Its initial orbit as it leaves the Earth would be a n about the Earth The escape velocity from the Earth is 11km s A Hyperbola velocities less than escape velocity produce elliptical orbits velocities greater than escape produce hyperbolic orbits 3 13 If a spaceship is launched from the Earth with a higher speed than the escape velocity it moves on a hyperbola A true 3 16 According to Kepler if P is the sidereal period of a planet A is the semi major axis of the planet s orbit aout the Sun and K is a constant then the relation among these is A P 2 K A 3 3 16 Kepler s first law says essentially that A The orbits of the planets are ellipses with the Sun at one focus 3 16 Kepler s second law says essentially that A The radius vector from the Sun to the planet sweeps out equal areas in equal times 3 16 If an asteroid has a sidereal period of eight years about the Sun its average distance from the Sun AU hint use Kepler s third law A 4 Kepler s 3rd Law P 2 A 3 earth s avg dist from sun is 1AU 3 18A Galileo is known for his A investigation of physical motions 3 18B Galileo is known for his A application of the telescope to astronomy 3 19 The statement for every force or action there is an equal and opposite reaction is the content of 3 19 Newton s second law states That for every action or force there is an equal and opposite reaction 3 19 Force equals mass times acceleration is a statement of A Newton s 3rd law A Wrong Newton s 3rd law A Newton s 2nd law 3 19 Newton s third law may be stated as the force on a body is equal to the product of its mass times its acceleration 3 19 The inverse square law for gravity was first proposed by Yuri Gagarin A false statement is the 2nd law A false by Issac Newton 3 19 The mass of an object is how strongly the Earth pulls on the object A false this would be its weight a force Mass indpt of where it is 3 19 Newton s third law states that for every action or force there is an equal and opposite reaction A correct A Newton 3 19 The inverse square law for the …