Understanding the Force of Gravity and Acceleration on a Planet's Surface"

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Homework Help Overview

The discussion revolves around calculating the acceleration due to gravity on the surface of a planet with a specified mass and radius. Participants explore the implications of mass and gravitational force in this context.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the formula for gravitational force and its relation to acceleration due to gravity, questioning the necessity of a second mass in calculations. Some express confusion about the net force and its role in determining acceleration.

Discussion Status

There is an ongoing exploration of the relationship between gravitational force and acceleration. Some participants have offered hints and clarifications regarding the use of Newton's law of gravity, while others are attempting to reconcile their understanding of the variables involved.

Contextual Notes

Participants are working under the assumption that they need to apply Newton's Universal Law of Gravity, and there is a discussion about the relevance of the mass of the object in relation to the acceleration due to gravity.

cary5
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What is the acceleration due to gravity on the surface of a planet with mass 5.00 x 1023 kg and radius 3.00 x 107 m? If you need to, suppose that a block of mass 50 kg is at rest on the surface. Why does it not matter what the mass of the block is?


a= Fnet/mass


i don't know the Fnet
 
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Hint: Newton's law of gravity.
 
Fg=G*m*m/r sqd
but that does not give me g and besids i need 2 masses for this
 
cary5 said:
Fg=G*m*m/r sqd
but that does not give me g and besids i need 2 masses for this
You have the mass of the planet--that's all you need. Use the equation from your first post.
 
Doc Al said:
You have the mass of the planet--that's all you need. Use the equation from your first post.

Fnet/5*1o^23=a ?
now i have 2 varabls
 
cary5 said:
Fnet/5*1o^23=a ?
now i have 2 varabls
No. Write the force of gravity on some mass m as:

Fg = G*M*m/r^2

where M is the mass of the planet

The acceleration due to gravity is Fg/m.
 
Doc Al said:
No. Write the force of gravity on some mass m as:

Fg = G*M*m/r^2

where M is the mass of the planet

The acceleration due to gravity is Fg/m.

Fg=(6.67*10^-11)(5.00*10^23)(m)/(3.00*10^7)^2
=0.037m
 
cary5 said:
Fg=(6.67*10^-11)(5.00*10^23)(m)/(3.00*10^7)^2
=0.037m
Sounds good to me. So what's the acceleration due to gravity?
 
Doc Al said:
Sounds good to me. So what's the acceleration due to gravity?

0.037m/5.0*10^23
=(7.4*10^-26)m
 
  • #10
cary5 said:
0.037m/5.0*10^23
=(7.4*10^-26)m
No. Go back to post #6. a = Fg/m (not Fg/M)
 
  • #11
cary5 said:
What is the acceleration due to gravity on the surface of a planet with mass 5.00 x 1023 kg and radius 3.00 x 107 m? If you need to, suppose that a block of mass 50 kg is at rest on the surface. Why does it not matter what the mass of the block is?a= Fnet/massi don't know the Fnet

Acceleration due to gravity is the same as the force of gravity for a 1 kg mass. For example, Earth's acceleration due to gravity is 9.8 m/s/s while its force for a one kg mass is 9.8 N. From this you can assume the second mass needed is one kg.

This allows you to use Newton's Universal Law of Gravity to isolate for Fg. If you used the second mass of the object as one, it should be the same for the acceleration due to gravity on that planet.
 
  • #12
barthayn said:
Acceleration due to gravity is the same as the force of gravity for a 1 kg mass. For example, Earth's acceleration due to gravity is 9.8 m/s/s while its force for a one kg mass is 9.8 N. From this you can assume the second mass needed is one kg.

This allows you to use Newton's Universal Law of Gravity to isolate for Fg. If you used the second mass of the object as one, it should be the same for the acceleration due to gravity on that planet.

ya that sounds good and it actuly makes sense
 

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