AST251H1 Lecture : lecture note

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salmondog80

22 Jan 2012

School

UTSG

Department

Astronomy & Astrophysics

Course

AST251H1

Professor

Susan Pfieffer

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Document Summary

Simpler to have sun in center occams razor, Kepler no move in circles but in ellipses, question why ellipses. Galielo saw the moons of jupiter, venus show faces. The laws of kepler, orbits sun on elliptical orbit in focus, move fastes closest to the sun, and slower further away, away is same over certain time same area, relation orbital period and distance, doestntell us how moons orbit. Newton, gravity more powerful, any two objects attract each other, with certain force depends on masses and idstance, inverse square, force between objects, 3 simple laws redict motion of a celestial bodies in the solar system, even moons however needed correction in the 20th century, more powerful predicts keplers and predicts for any object. It works but how, mercury doesn t move like it should, newtons law didn t work first time, Energy, kinetic energy, potrential energy, radiation, all can be converted into each other,

Related Questions

Select the one that is not one of Newton's Law of motion.

A) equal and opposite reaction force acts for each action.

B) An object in uniform motion in the absence of external force continues to move in the same direction.

C) Rate of change of momentum is equal to the net force applied

D) The body has some masses attract each other with a constant force.

Newton’s version of Kepler’s third law offers one of the few ways of determining the mass of objects in space. One form of this relationship is expressed in Equation 7.6. To derive it, however, we assumed the orbit of the less massive object is circular and is centered on the more massive object, which is not completely realistic. In reality, both objects move in an orbit in response to the gravitational force between them! A careful derivation shows that for two masses and in orbit around one another with semimajor axis a, the proper expression of Newton’s version of Kepler’s third law is

yellowbeetle927

a.) A hockey puck is observed to be sliding along a flatfrictionless surface at a speed of 4 cm/min. There is no net forceacting on the puck. Assuming it doesn't smash into anything, howfast will the puck be going 17 min later?
cm/min

b.) An object is accelerating. Which one of the followingstatements is true?
The object must be speeding up.
Gravity must be causing the object to accelerate.
The object must be changing directions.
The object must be slowing down.
There is a net force acting on the object.

c.) A 100 kg block weighs 220 lb on Earth. If the block weretransported to a planetary body that had a smaller free fallacceleration (as compared to Earth), which one of the followingwould be true?
The block would have the same weight and a smaller mass.
The block would have the same mass and a bigger weight.
The block would have the same mass and the same weight.
The block would have the same weight and a bigger mass.
The block would have the same mass and a smaller weight.
d.) What does it mean (in physics) to say that a quantity isconserved?
It means that the quantity is not being used.
It means the total amount is zero.
It means the total amount never changes.
It means it's being saved up.

e.) At a certain point in time, the total energy of a closed systemis observed to be 176 J. Which one of the following statements istrue?
Three hours later the energy of the system is 352 J.
Four hours later the energy of the system is 88 J.
All of the energy must be kinetic if the objects are moving.
Twelve hours later the energy of the system is 176 J.
Some of the energy must be potential.

g.) Which of the following statements are impossible? Choose allthat apply.
The parked truck had 8770 J of KE.
The scooter had 0 J of KE and 0 kgÂ·m/s of momentum.
A ball moving in a circle had 0 N of net force acting on it.
A box had an acceleration of 0 m/s2 while a net force of 311 Nacted on it.
Jack exerted 18 N of force due east on a cart. As a direct result,the cart exerted 18 N of force due west upon Jack.
A toothpick exerts a smaller gravitational force upon the Moon thanthe Moon exerts upon it.

a.) Two balls make up a closed system. Ball A has 701 J of energyand ball B has 78 J. After they collide, ball A has 665 J. How muchenergy does ball B have after they collide?
J

b.) An asteroid and a comet collide head on. Prior to thecollision, the asteroid has a momentum of 700,000 kgÂ·m/s up and thecomet has a momentum of 800,000 kgÂ·m/s down. After the collisionthe asteroid has a momentum of 750,000 kgÂ·m/s down. After thecollision, what is the comet's momentum?
kgÂ·m/s
North
South
East
West
Up
Down
Left
Right
No direction because the comet has stopped

c.) How much does a 28 kg object weigh on Moon? Please feel free toreference the Solar System Data table located at the beginning ofUnit II.
______N

d.) A 660 N net force acts on a 42 kg object. Determine theobject's acceleration.
_____m/s2

e.) Calculate the gravitational force between a 657 kg object(resting on Earth) and the Moon. The mass of the Moon is 7.347Ã1022kg and the distance between the object & the Moon is 3.844Ã108m.
____N

AST251H1 Lecture : lecture note

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