Physics circular motion, orbits, and gravity

AI Thread Summary
Bert and Ernie are stationary at different distances from a star, leading to varying gravitational forces acting on them. The discussion revolves around the true or false nature of several statements regarding their weights and accelerations compared to Big Bird, who is in orbit. It is established that Bert's weight is indeed 9 times greater than Ernie's due to the inverse square law of gravitation. Big Bird's acceleration is zero while in orbit, and the gravitational force Bert feels is 9 times greater than Ernie's, confirming the relationship between distance and gravitational force. Overall, the participants clarify their understanding of gravitational principles and centripetal force in relation to the scenario.
thesandalman
Messages
11
Reaction score
0

Homework Statement



ics
Consider identical twins named Bert and Ernie who are visiting a star named Alpha Sesame. Bert is at a distance r from the star while Ernie is located a distance 3r. Both Bert and Ernie are stationary (they are standing on platforms built by an alien super race) and are not orbiting the star. Big Bird, who has the same mass as Bert and Ernie despite his larger volume, flies by Bert in a spaceship which is in a circular orbit or radius r around Alpha Sesame.

All Answers are true or false:

-If Bert and Ernie would step on bathroom scales, Bert's weight would be 9 times larger than Ernie's.
-If Bert were to step off the platform and fall toward the star, he would experience an identical acceleration to that of Big Bird.
-If Big Bird were to step on a bathroom scale in the spaceship, the scale would register zero.
-Big Bird's acceleration is zero.
-The gravitational force that Bert feels is 3 times larger than the gravitational force Ernie feels.



Homework Equations






The Attempt at a Solution



I know the third answer to be true. I believe the fourth question is false due to gravity. Not so sure about the other ones. That is where I need the help!
 
Physics news on Phys.org
For this question you need to look at Newton's law of universal gravitation,
F=(Gm1m2)/r^2. Also, take a look at centripetal force, F=(m*V^2)/R.
That should get you started.
 
Ok, here is what I am thinking:
Question 1 is true due to the fact that force is 1/9 or therefore 9 times the weight. Question 2 i also say is true because the same force would be acting on both big bird in orbit and Burt when he falls off the platform.
Question 3 I know is true because they are in the equlibrium.
Question 4 is False due to gravity.
Question 5 is true due to this equation F=(Gm1m2)/r^2.

Am I on the right track?
 
I agree with your answer for question number one, since the relation between the distances is squared. Question two seems ok also. I don’t understand question 3.
Number four is correct there is an acceleration. I don’t agree with number 5 because if you look at F=(Gm1m2)/r^2, Bert feels a gravitational force 9 times greater, the term in r^2.
 
Thanks you so very much for your help! I really appreciate it! You were correct by the way.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'
Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is(Figure 2): F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top