Ly on gravitation only one part

  • Thread starter squintyeyes
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In summary, the conversation discusses a problem involving a comet's speed in different distances from the sun. The comet travels in elliptical orbits with large eccentricities. The attempt to solve the problem using conservation of momentum is incorrect and conservation of energy is suggested instead. However, there is a need to know the mass of the comet in order to complete the calculation.
  • #1
squintyeyes
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urgently need help on gravitation only one part

Comets travel around the sun in elliptical orbits with large eccentricities. If a comet has speed 7.0 x 10^4 m/s when at a distance of 2.5 x 10^11 m from the center of the sun, what is its speed when at a distance of 9.0 * 10^10 m?
___________ m/s

Attempt
(7.0 x 10^4)(2.5 x 10^11)= v(9.0 * 10^10)
v = 194444.444

However, this answer was marked wrong.
 
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  • #2


First: in what units is your v given?

The angular momentum is constant along the orbit, but its magnitude is r*v* sin(angle between the radius and the direction of the velocity). This angle is unknown. So use the conservation of momentum instead.

ehild
 
  • #3


v is in m/s. And what do you mean by saying that i should use coservation of momentum. Isn't that what i did but it was marked wrong?
 
  • #4


Sorry, I meant conservation of energy...

ehild
 
  • #5


okay but if i use conservation of energy i still encounter a problem.

KE + PE = KE +PE
1/2mv^2 + (-GMm/r) = 1/2mV^2 + (-GMm/R)
1/2v^2 + (-GM/r) = 1/2V^2 + (-GM/R)

I know
v = 2 x 10^4 m/s
r= 3 x 10^11 m
R=4 x 10^10 m

but i still need to know what M, the mass of the comet is equal to.
 
  • #6


Isn't M the mass of the sun?
 

1. What is "Ly on gravitation only one part"?

"Ly on gravitation only one part" refers to the concept of using the distance unit "light-year" (Ly) to measure gravitational force between two objects, assuming that only one of the objects is contributing to the force.

2. How is "Ly on gravitation only one part" related to Newton's law of gravitation?

Newton's law of gravitation states that the force of gravitational attraction between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. "Ly on gravitation only one part" is a unit of distance used in this equation to measure the distance between the two objects.

3. Can "Ly on gravitation only one part" be used to measure gravitational force accurately?

Yes, "Ly on gravitation only one part" can be used to measure gravitational force accurately as long as the distance between the two objects is large enough for the effects of other factors, such as the gravitational pull of other nearby objects, to be negligible.

4. Why is "Ly on gravitation only one part" a useful unit of distance for measuring gravitational force?

"Ly on gravitation only one part" is a useful unit of distance because it allows for large distances to be measured efficiently. For example, the distance between the Earth and the Sun is approximately 8 light-minutes, while the distance between the Earth and the nearest star is approximately 4 light-years. Using "Ly on gravitation only one part" allows for these distances to be expressed in a more manageable and comprehensible way.

5. How does using "Ly on gravitation only one part" affect our understanding of the universe?

Using "Ly on gravitation only one part" as a unit of distance in measuring gravitational force allows us to better understand the vast distances and forces at play in the universe. It also allows for more accurate calculations and predictions in fields such as astronomy and astrophysics.

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