All Questions
Tagged with gravity newtonian-mechanics
317
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What is a simple example that contradicts the theory that light (photons) could have a super small mass? [duplicate]
The obvious example is that, to bring something that has mass to the speed $c$ requires infinite energy due to special relativity. But what if a kid asked me "What if light/photos had a super ...
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3
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75
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How much time does it take for an object to fall from space? [closed]
Let's say there's an object of mass $m$ in space, $h$ meters away from the surface of the Earth. $h$ is large enough that $g$ cannot be assumed to be constant. The acceleration varies according to ...
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2
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Why does a ball bounce back even when it is released and not thrown?
So according to my understanding when we thrown a ball towards ground we apply an additional amount of force which results in an acceleration greater than the one due to earth. When this ball reaches ...
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1
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How does a mass that's dropped when strung by an inelastic, slack string continue its motion? [closed]
Say a mass is connected to a light, inextensible string of length $l$. The other end of the string is fixed to a point O. If initially, the mass is kept at a horizontal distance of $\frac {l}{2}$to ...
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How does gravity act and propagate in a 2+1D universe?—Newtonian versus general relativity
In a hypothetical 2+1D universe:
if we apply the Newtonian concept of gravity, we might expect that the gravitational force between two mass points with a distance of $r$ would diminish linearly with ...
- 618
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2
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33
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Understanding conservation of angular momentum in relation with rotating objects
Conservation of angular momentum says that the angular momentum of a closed system will not change if there is no external torque applied to the system. For example, let's take the example of a ...
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55
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What is the locus of the velocity vectors of a spaceship moving in some distance from a black hole?
Someone with a background in mathematics and limited knowledge of physics asks the following question:
Starting from rest, a spaceship is momentarily pushed with a specific amount of kinetic energy in ...
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How much kinetic energy would a star in a galaxy have if it fell to the center?
I want to calculate the speed, or equivalently, the kinetic energy of a star, if it had no rotational speed and fell from a given radius to the center of the galaxy.
I assume Newton's shell theorem ...
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Describe the decrease in potential energy if two forces are acting on it one conservative which is greater than other applied by us in opposite dirn [closed]
So imagine this situation.
An object is experiencing two forces, one due to gravity in downward direction and other applied by us in upward direction such that our force is less than gravitational ...
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Why are my heavier objects sliding on a smaller incline than lighter objects? Coefficient of Static Friction
I gave my students a lab on the coefficient of friction in 2D. I use a wooden plank and sandpaper as my IV. I have done this experiment in a few different ways, but the normal consensus was still the ...
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How a force that is always perpendicular to velocity can change the kinetic energy when another force is acting oppposite to velocity? [closed]
When a satellite is revolving around a planet with an orbital velocity in presence of air resistance, the satellite's Kinetic Energy keeps on increasing as it falls down. The resistive force is trying ...
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How to calculate the period of non-circular orbits?
How to calculate the period of non-circular orbits?
By conservation of mechanical energy:
$$
E = -\frac{GMm}{r} + \frac{1}{2}\mu \left ( \dot{r}^2 + r^2 \dot{\theta}^2 \right )
$$
By the conservation ...
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23
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Does a ball striking ground with different forces contradict Newton's Second law of Motion? [duplicate]
The second law says that
$$F = ma$$
Let's assume that a ball is dropped and it strikes the ground with a force. And the process is repeated albeit from a greater height.
To calculate the force, we ...
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3
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109
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Gravitational potential energy of pendulum below pivot [closed]
The author wants to write potential energy of the ball attached to pendulum. He says that pivot is at $y=0$, so $y$ component is $-\ell\cos\vartheta$ so $U=-mg\ell\cos\vartheta$.
But why don't we ...
- 137
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2 Masses on a table confusion - Normal force and weight
Forces up are greater than forces down. However, the masses on the table obviously don't start flying upwards. Am I missing a force here?
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Do objects with non-uniform shapes and mass distributions rotate as a result of gravitational attraction?
I was thinking about orbital mechanics this morning and a question arose: do objects with non-uniform shapes and mass distributions rotate as a result of gravitational attraction?
Thinking through the ...
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As the speed time graph for a body thrown vertically upwards is not differentiable at the top point so why acc. is taken as 9.8 m/s² at the top point?
In the shown speed - time graph for a body thrown vertically up there is a sharp kink in the graph at the instant for which body is at highest position ie not differentiable so we can't find ...
- 1,357
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Quantifying the eastwards motion of an object in free-fall on the equator
I've been reviewing the correspondence between Hooke and Newton, trying to understand how an object falls eastwards, as predicted by Galileo as well. I've read two things:
As an object falls, it ...
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Well I dont know, what you want? [closed]
When you calculate the gravitational force $F_G = G \cdot\frac{m\cdot M}{r^2}$.
Is this equation precise for relativistic big masses, given that $m$ and $M$ do not and can not move?
If not is there an ...
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How to create a more accurate gravity simulation? [duplicate]
Goal:
I am interested creating a simple gravity simulation and was wondering if it was possible to describe two objects motions through time with percision. All other parameters are known (...
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1
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87
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Does weightlessness make no difference to free fall?
I looked up a lot of articles and questions about free fall motion and weightlessness. And I know there are a lot of similar questions.
In conclusion, I understand that there is no way to distinguish ...
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Gravity, orbiting bodies and Newton’s second law of motion [duplicate]
As I understand it an object travelling in a circular motion is undergoing a centripetal ‘force’. As Newton’s second law of motion, put in simple terms states that a moving object will tend to ...
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Work done on a body and work done by the body
I want to know that, if we suppose that, if a ball is falling freely then work would be done on the ball by gravity so energy would be given to the ball? and when the ball rebounds after striking the ...
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Is this equation of vector form of gravity correct? [closed]
There is this equation in my physics book about gravity as a form of vector. It initially confused me, but after doing a bit of research, I suppose $\hat{r}$ should be replaced by $\vec{r}$
Am I ...
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Do expanding mass shells gain energy?
I've found an article which says in section 2
an expanding gravitational system of given mass gains energy
Does an expanding gravitational system or an expanding shell of a given mass gain energy as ...
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When you drop a feather from high off the ground, when it gets near the ground, how will its speed have changed?
When an object falls, it should fall faster and faster because of gravitational acceleration. But when we are talking about a feather, we have to talk about air resistance. Air resistance is ...
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2
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157
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Does a hot object have more gravity than a cold object - conflicting views [closed]
In this similar question the answer says that because of relativity e=mc^2 a hot object has greater mass/energy therefore has greater gravity than a cold object.
But:
In Experiment on the Relationship ...
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Trying to estimate the path of a projectile with equations on graphic calculator. Need help
When a projectile is released with a very high velocity, it will not follow basic projectile motion because the Earth’s curvature will hinder those equations. In a crude sense, the Earth will curve ...
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355
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How does a screw roll down an inclined plane? [closed]
I was thinking about how various objects would slide down on an inclined plane, and I just couldn't figure this problem out.
So let's say I have this screw or cone on its side, on an inclined plane. ...
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2
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Angle of projection for the minimum time of flight for a given range
If a projectile has to cover a fixed range under gravity, then what should be the angle of projection for the total time of flight to be minimum?
The initial and final point of the projectile are both ...
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How does the collapse of a spherical cloud of point-masses look in the Newtonian framework?
Imagine a spherically symmetric cloud of point masses, without angular momentum, interacting by gravity only.
If we examine this process within a Newtonian framework, the particles accelerate towards ...
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Does the force that need to be applied to pull the weight out of a well by string is more at the start?
One way to estimate depth of the well is attaching a weight to a string then throwing it into the well until it touch a hard surface then pulling the string out of the well and evaluate its length.
...
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163
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Circular velocity vector on the surface of spherical potential (gravity)
So, I would like to integrate paths of particles on circular velocity on the surface of a sphere (due to some potential, i.e. gravity).
The problem is to fix the two angular velocities $\dot \theta $ ...
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Difference between geodesics on surfaces and paths under gravitiational fields
Sorry for the maybe silly question, but I'm a math student and I'm not able to find the answer to this question from the physics point of view.
Let us suppose that a ball is set in a non equilibrium ...
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Initial velocity of a body when the distance travelled by it in the last second before reaching its maximum height is $5\ \textrm{m}$ [closed]
I stumbled upon this problem recently, and it has been haunting me for more than a day at this point. The question is as follows:-
When a ball is thrown up, it reaches a maximum height of $h$, ...
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328
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Do black holes exert infinite forces?
Black holes have infinite mass so according to Newton's law of universal gravitation should exert and infinite amount of gravity force.
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In two particle system why can't we calculate the gravitational potential energy of each mass separately and find the net potential energy?
In a two particle system, suppose both are moving by their internal gravitational force, and hence the potential energies of the system is changing. Since both are acted upon by the conservative ...
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Gravity Differential Equations
I was just messing around with Newton's Law of gravitation, when I had the idea of converting Newton's Law into differential form (more or less like Maxwell's equations).
I did the following:
#1 ...
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3
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How velocity affects different orbits?
Assume a sun with mass $M$ and a planet with mass $m$. Assume at $t_0$ the planet is $r_0$ (distance) away from sun and has an initial velocity of $v_0$. Also, let’s assume the angle between the $r_0$ ...
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If contact forces are repulsive then how are we able to pull stuff? [closed]
I searched a lot on internet(especially physics stackexchange) about the nature of contact forces. I came to know through most of them that it is repulsive in nature which surely means that your hand ...
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How fast would a rocket have to go to maintain in the earth orbit without falling down? And how frequent would rocket boosters be needed? [closed]
I was thinking how fast would a rocket have to go to maintain in the in earth orbit? I was thinking of the ISS going 7000kph with rocket boosters every 6 months. What is the most efficient way to ...
user333418
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Dropping a ball with increasing masses and measuring the time until it no longer bounces
How could one theoretically explain that when one drops several balls with different masses from the hand, the bounces are less if the ball has larger mass and comes to rest after a shorter period of ...
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555
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How can the orbital motion of planets around the sun be calculated taking into account the force exerted by other planets?
In The Feynman Lectures on Physics (Vol. 1, Chapter 9), Feynman explained how to calculate the planetary motion by just using the Newton's laws of motion and the Euler's method as a numerical solution ...
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How can weight be equal in the equivalence principle?
According to Einstein, weight will be the same as here in earth in a rocket going at 1G far from gravity fields. If we propulse an object here it will feel two forces, F=mg and F=ma of the thrust, but ...
user189508
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What is the gravitational force of a intangible sphere inside another sphere?
This is similar to the problem of the gravitational force of a particle inside a sphere, but instead of a particle, I want to know how two objects of non-negligible size and mass would interact ...
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How can a person inside from a veiled and free-falling elevator distinguish whether he is in an inertial or non-inertial frame?
From wikipedia: "A non-inertial reference frame is a frame of reference that undergoes acceleration with respect to an inertial frame", according to that statement, I would say that an ...
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If gravity is not a force then why Newton's first 2 laws contradict each other?
I know Newton's laws especially the 1st and 2nd laws of motion:
1st law: object in motion stays in motion unless it is influenced by an outside force.
2nd law: F=ma
So Gravity is not a force, then ...
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What will be the tension force in this case?
Suppose I have a block of mass $2\, {\rm kg}$ sitting on my table. Then I connect a string to it and pull it vertically upwards. The resultant acceleration is vertically upwards: $2.2\, {\rm ms}^{-2}$....
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Conceptual Question: What would happen to satellites orbiting the earth if mass of earth suddenly increases? [closed]
Would the satellite crash onto the earth? If so, why, and in what kind of motion? A spiral motion sounds intuitive, but why?
Or there is another possibility: will the satellite continue to execute ...
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174
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Inertia of an elevator
Imagine a situation where we have a relatively light empty elevator moving up at a pretty high constant velocity say something above $10\ m/s$, just so that it has a considerable amount of momentum ...
