Gravitational force - MCQ question Watch

DanielDaniels
Badges: 14
Rep:
?
#1
Report Thread starter 4 years ago
#1
There was one question in my exam paper that am keen to understand and know what's the correct answer is.

So here's the question:

which of the following does NOT affect the gravitational force on a person.
1. Mass of the Earth
2. Mass of the person
3. Rate of rotation of the earth
4. The position of the person.

^ I selected the position of the person option 4
0
reply
Stonebridge
Badges: 10
#2
Report 4 years ago
#2
(Original post by Daniel Atieh)
There was one question in my exam paper that am keen to understand and know what's the correct answer is.

So here's the question:

which of the following does NOT affect the gravitational force on a person.
1. Mass of the Earth
2. Mass of the person
3. Rate of rotation of the earth
4. The position of the person.

^ I selected the position of the person option 4

From

F=G\frac{M_e M_p}{r^2}

which of those 4 does not appear in the formula?
reply
DanielDaniels
Badges: 14
Rep:
?
#3
Report Thread starter 4 years ago
#3
(Original post by Stonebridge)
From

F=G\frac{M_e M_p}{r^2}

which of those 4 does not appear in the formula?
but in F=mv^2 /r
does v here imply to the rate of rotation?
I dont know if they meant the position on the surface or not.

Thats how i thought about it in the exam, so where did i go wrong? I am trying to learn from my mistakes.

Thank you.
0
reply
Stonebridge
Badges: 10
#4
Report 4 years ago
#4
(Original post by Daniel Atieh)
but in F=mv^2 /r
does v here imply to the rate of rotation?
I dont know if they meant the position on the surface or not.

Thats how i thought about it in the exam, so where did i go wrong? I am trying to learn from my mistakes.

Thank you.

The equation you have quoted above is not the equation for the gravitational force of one object on another, which is what the question is asking. The gravitational force on an object is determined by Newton's equation, which I quoted in my post. Your equation is about centripetal force. Yes v is the speed of rotation, but that has no effect on the actual gravitational force, which is given by Newton's equation.

The mistake you are making is to grab at formulas without thinking about the physics behind them, and what they mean.

The gravitation force of one object on another depends on
1. the mass of object 1 (Earth)
2. the mass of object 2 (person)
3. the distance between them (position of one relative to the other)
4. G - which was not included in the options.

You are attracted to the centre of the Earth by a force given by Newton's equation whether the Earth spins or not.
What does happen, when the Earth spins, is that this gravitational force has to provide some or all of the centripetal force to move you in a circle. The gravitational force doesn't change, but the centripetal force can.
reply
DanielDaniels
Badges: 14
Rep:
?
#5
Report Thread starter 4 years ago
#5
(Original post by Stonebridge)
The equation you have quoted above is not the equation for the gravitational force of one object on another, which is what the question is asking. The gravitational force on an object is determined by Newton's equation, which I quoted in my post. Your equation is about centripetal force. Yes v is the speed of rotation, but that has no effect on the actual gravitational force, which is given by Newton's equation.

The mistake you are making is to grab at formulas without thinking about the physics behind them, and what they mean.

The gravitation force of one object on another depends on
1. the mass of object 1 (Earth)
2. the mass of object 2 (person)
3. the distance between them (position of one relative to the other)
4. G - which was not included in the options.

You are attracted to the centre of the Earth by a force given by Newton's equation whether the Earth spins or not.
What does happen, when the Earth spins, is that this gravitational force has to provide some or all of the centripetal force to move you in a circle. The gravitational force doesn't change, but the centripetal force can.
THANKS A MILLION SERIOUSLY!!
You really helped me a lot and inspired me! I'm grateful to you, man!
I hope i can score A/A* in physics, lets see my luck.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of Birmingham
    Postgraduate Open Day Postgraduate
    Wed, 20 Mar '19
  • King's College London
    Postgraduate Taught Courses - Arts & Sciences - Strand Campus Postgraduate
    Wed, 20 Mar '19
  • University of East Anglia
    All Departments Open 13:00-17:00. Find out more about our diverse range of subject areas and career progression in the Arts & Humanities, Social Sciences, Medicine & Health Sciences, and the Sciences. Postgraduate
    Wed, 20 Mar '19

Where do you need more help?

Which Uni should I go to? (59)
14.94%
How successful will I become if I take my planned subjects? (38)
9.62%
How happy will I be if I take this career? (74)
18.73%
How do I achieve my dream Uni placement? (59)
14.94%
What should I study to achieve my dream career? (44)
11.14%
How can I be the best version of myself? (121)
30.63%

Watched Threads

View All