Conceptual problem: Finding gravitational KE

AI Thread Summary
To find the kinetic energy (KE) of an orbiting body, both the formulas 1/2mv^2 and 1/2Gm1m2/r can be used, depending on convenience. In a circular orbit, gravitational force acts as the centripetal force, leading to the relationship mv^2/r = GMm/r^2. This simplifies to 0.5mv^2 = 0.5GMm/r, indicating that kinetic energy can be derived from gravitational potential energy (GPE). The total energy of the orbiting body is expressed as KE + GPE = -0.5GMm/r, highlighting the interplay between these two forms of energy in orbital mechanics. Understanding these relationships is crucial for solving problems related to gravitational systems.
grantP
Messages
19
Reaction score
0

Homework Statement



to find KE of an orbiting body, do I use 1/2mv^2 or 1/2Gm1m2/r??

Homework Equations


The Attempt at a Solution

 
Physics news on Phys.org
Hi grantP,

grantP said:

Homework Statement



to find KE of an orbiting body, do I use 1/2mv^2 or 1/2Gm1m2/r??

If it's a circular orbit (for example) then it would just depend on which is more convenient for the problem.
 
For an orbiting body, gravitational force provides for the centripetal force:

mv2/r = GMm/r2


0.5mv2 = 0.5GMm/r


Just to digress abit, so the total energy an orbiting body with distance r away from the centre of the planet is:

KE + GPE = 0.5GMm/r + (-GMm/r)

= -0.5GMm/r
 

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
View full post »

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »

Similar threads

Homework help: Work and Energy: Spring
Replies
3
Views
1K
What Is the Kinetic Energy of a Proton at 1/4 the Speed of Light?
Replies
3
Views
2K
Finding kinetic energy and initial velocity of a cart over time
Replies
6
Views
2K
Do A and C have same or different KE at the end?
Replies
3
Views
1K
Moving Down a Ramp: Answers & Explanations
Replies
8
Views
2K
Velocity of a hollow cylinder at the bottom of an incline
Replies
9
Views
4K
Why is the Work Zero on a Frictionless Surface?
Replies
6
Views
2K
Calculating Potential Energy Change for a Mountain Climber
Replies
2
Views
1K
Calculate Mass of Satellite: Step-by-Step Guide
Replies
16
Views
3K
Calculating Velocity at the Bottom of a Quarter Circle Track
Replies
8
Views
3K

Hot Threads

Recent Insights

Back
Top