Newtonian mechanics covers the discussion of the movement of classical bodies under the influence of forces by making use of Newton’s three laws. For more general discussion of energy, momentum conservation etc., use classical-mechanics, for Newton’s description of gravity, use newtonian-gravity.

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How is a ballistic pendulum affected by two objects with different mass?

Imagine that bullet A (made of lead) has twice the mass of bullet B It is shot at the same muzzle velocity as bullet B onto a ballistic pendulum; all other initial variables are the same: size and ...
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0answers
44 views

Total angular momentum of a continuous body

I find the definition of total angular momentum $\mathbf{L}$ of a system of $n$ material points with respect to a given point $Q$ as the sum of the momenta $\ell_i=\mathbf{r}_i\times\mathbf{p}_i$ ...
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0answers
38 views

The behaviour that saves more energy/ petrol when driving down-up-hill [closed]

This question is in a way a follow-up of this one: Can a car get better mileage driving over hills?, it is similar to that, is no engineering question and is in no way a homework problem, I'd like you ...
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1answer
44 views

Normal force on a banked road & why it's larger than the gravitational force here

Please read this: http://www.askiitians.com/iit-jee-physics/mechanics/banking-of-roads.aspx From my understanding of normal forces, they are a reaction to gravitational or other forces. When a force ...
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2answers
316 views

Relative motion. Setting course of closest approach

Let $r_{P/Q}$ be the position vector of $\overrightarrow P$ relative to vector $\overrightarrow Q$ and $v_{P/Q}$ the velocity vector of $\overrightarrow P$ relative to $\overrightarrow Q$. Suppose ...
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4answers
2k views

Does a truck stop faster if the stack on the back of truck is stable or if it moves forward?

My question in the title might not be very descriptive so I am re-writing it here: If there is a truck in motion and it has stack of hay (lets suppose) on the back. Now if the truck comes to a sudden ...
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1answer
66 views

Analysis of a card pyramid

Here's an interesting question I thought of. Firstly, picture one of those card pyramids. Hopefully you know what I'm taking about when I say card pyramid, but basically you balance two cards up ...
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3answers
51 views

An elevator accelerating upward, tension increases in the rope to which a fish hangs inside the elevator why?

A fish is hanging in an elevator through a rope, when elevator accelerates upward the tension in the rope increases why? When elevator accelerates downward the tension in the rope decreases why?
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1answer
63 views

Are there any exceptions for law of conservation of angular momentum?

I just wrote a medical entrance test, in which this question appeared a person sitting firmly over a rotating stool has his arms stretched, if he folds his arms, angular momentum about the axis of ...
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1answer
153 views

Calculate orbit height from tangential velocity

Is it possible to calculate the altitude of a satellite orbiting a planet, just from the planet's mass and the satellite's velocity, assuming that the satellite is in a perfect circular orbit? If so, ...
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1answer
293 views

Coriolis deflection:- is it 4 times if the object is thrown up, compared to a drop?

A particle is thrown up vertically with initial speed, reaches a maximum height and falls back to ground. Show that the Coriolis deflection when it again reaches the ground is opposite in ...
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3answers
1k views

Looking for an intuitive understanding of normal force

I understand normal force to be the perpendicular force to a surface of contact. However, I have come across a problem which has caused me to rethink this. My initial understanding of force is ...
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2answers
85 views

Proof of Newton's second law [duplicate]

Is it possible to prove Newton's second law of motion, $F=ma$? Or is it just realized because of proportionality and the definition of a Newton of force?
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2answers
143 views

Dropping a weight onto a spring scale

Say I drop a 5kg weight from a height of 1 meters onto a spring scale like many people have in their bathrooms. On impact the scale will show a higher weight than 5kg. Question: Which quantities ...
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0answers
19 views

Spring limitation

Is there any limitation in acceleration and frequency of a spring. Please, imagine a horizontal spring with an object of mass $m$ attached in the free side and the friction is neglected. ...
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5answers
989 views

Electron shells in atoms: What causes them to exist as they do?

I have seen similar posts, but I haven't seen what seems to be a clear and direct answer. Why do only a certain number of electrons occupy each shell? Why are the shells arranged in certain distances ...
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2answers
54 views

Why does friction act on a cylinder rolling on an inclined?

When a cylinder performs pure rolling while on an inclined plane, Why does friction act on the bottom point? In pure rolling the bottom most point is at rest, so there is no sliding over ...
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2answers
132 views

If Earth and Jupiter are orbiting around Sun in same orbit, will they have same time period?

Let us suppose that Earth and Jupiter are orbiting around the Sun in same orbit, If we talk about at any particular point. (Which is not possible but for the sake of question) I was wondering that ...
2
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1answer
100 views

Weightless person in a cart on a rail [closed]

In a problem I'm trying to solve I'm having a conflict between my understanding and the proposed solution of the problem. In the problem, a cart of mass $m$ is put at rest in the start of a ...
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0answers
25 views

Mechanics - Rotational Inertia [migrated]

I am facing a problem solving a mechanical system which is shown in the scheme below. We assume that coupling of the two shafts is done with a clutch Equations: ...
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1answer
70 views

Why doesn't atmospheric pressure crush thick walled structures?

There is one thing that puzzles me: common explanation of why don't structures collapse under the enormous atmospheric pressure (~101300N/m^2) is that the force pushing from inside balances out the ...
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1answer
52 views

Determining straining force and reaction forces on a beam [closed]

A homogenous beam $OA$ with the length $4a$ and the mass $m$ can rotate in the vertical plane along a horizontal axis through $O$ and is kept in equilibrium by a wire running from the points A and C ...
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2answers
81 views

Is there a normal downward force here?

Now through my understanding, there is a weight force that points downward on block A, also another weight force that points downward on block B. Between block A and block B, there is two normal ...
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1answer
64 views

Two equations for $y$ in projectile motions

I have two equations on my equation sheet: $$y=v_o t \sin \theta - \frac{1}{2} g t^2.$$ $$y_{\max} = \frac{v_o^2 \sin^2\theta }{2g}.$$ I understand that the first one is an equation for the height ...
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0answers
71 views

Interesting approach to Kepler problem

I won't go into the explanation of this idea, because it is explained in this blog post. In this paper, which was featured on John Baez's blog, $\frac {dt}{d\lambda}$ is given as $\frac r V$, where ...
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1answer
440 views

Relative wind velocity explanation - understanding Irodov problem 1.6

I am having trouble understanding the reasoning behind the solution in this Irodov General Physics problem. The problem is 1.6: 1.6. A ship moves along the equator to the east with velocity vo = ...
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6answers
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Can you ever exert more downwards force than your weight?

So, because I'm a hardcore person, I risked all this afternoon by going out in the wind, the rain and the cold to construct a willow den. Yes, it seems a menial task, but it was actually quite ...
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3answers
412 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
4
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1answer
73 views

General construction of equations of motion for free particles

I've got a question regarding the different Symmetrie-Lie-Groups of Newtonian Mechanics and special realtivity. Is there a canonical way to obtain the equations of motion for a free particle only by ...
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1answer
141 views

Spring Stiffness Calculation Problems

This may sound like a trivial question but please hear me out. I am trying to model a 1 DoF electromagnetic vibration sensor (geophone) analytically and with finite elements. A geophone consists of ...
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2answers
45 views

Centre of mass of a system of particles

If the centre of mass of a system of particles is at the origin, does this mean that if there is a particle on the positive X-axis, there must be atleast one particle on the negative X-axis? I feel ...
1
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1answer
717 views

1D Kinematics - Relative Motion involving non-inertial frames of reference

I recently came across a question involving non-inertial frames of reference. I didn't quite understand the way it had been solved due to some conceptual confusion regarding certain deductions made to ...
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1answer
33 views

Angular velocity in central force field

For motion in a central force field consider a rotating reference frame, which is characterized by the Euler angles $\alpha$, $\beta$, $\gamma$ associated with the rotation of the frame of Cartesian ...
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1answer
47 views

Newton's Third law of motion: A hammer hits a wall vs. hits a tire

When we hit the wall by a hammer, Newton’s third law says that hammer applies force on the wall (action) and wall applies force on hammer (reaction) equal in magnitude but opposite in direction ok ...
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1answer
41 views

Average force for repeated elastic collisions

I was asked to compute the average force exerted by a rigid spherical ball (mass $m$) on the floor over time $t \rightarrow \infty$, in a situation where the ball is dropped vertically from a height ...
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7answers
10k views

Can we theoretically balance a perfectly symmetrical pencil on its one-atom tip?

I was asked by an undergrad student about this question. I think if we were to take away air molecules around the pencil and cool it to absolute zero, that pencil would theoretically balance. Am I ...
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1answer
23 views

Inertia of a body cancells some amount of force?

If we have a block on a frictionless surface and we apply force F on the block to accelerate it, some amount of applied force will be cancelled by the inertia of the block am I right?
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1answer
92 views

Very confused about effective spring constant

I know that for springs in parallel, the effective spring constant is $k_1+k_2$ and for springs in series the constant is $1/(1/k_1+1/k_2)$. But there are some weird problems where finding the ...
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2answers
15k views

How is distance between sun and earth calculated?

How has the distance between sun and earth been calculated? Also what is the size of the sun?
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3answers
122 views

Distance traveled by a water jet

I helped my kid in a science fair project, where we punctured holes in a water bottle at various heights and then measured the distance traveled by the water jets before they hit the ground. The ...
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0answers
33 views

Free body driagram of box and plate with a friction force on a smooth surface

On a smooth surface we have a plate of 40 kg and on that plate a a box of 10 kg. Between the plate and the box there is a ...
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1answer
40 views

Newton's law for rigid bodies

Is newton's third law valid for rigid bodies? Say, if we have a bullet hit on a rod which is vertically placed on a rough floor. Friction is just sufficient sp that the rod rotates and does not ...
1
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1answer
532 views

The choice of pivot point in non-equilibrium scenarios [duplicate]

It is true that under equilibrium condition, no matter what pivot point one choose, the resulting net torque will always be zero. I wonder if this principle apply to non-equilibrium scenarios as well, ...
2
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2answers
41 views

Resulting force when bending plywood

My sister and I are working on a thesis in interior design on a plywood chair similar to the picture, where the red part bends. We are trying to work out how much the plywood would push back when a ...
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1answer
567 views

A moving inclined plane with block problem

I'm trying to solve for a challenging problem : a moving inclined plane with a block I want to solve for the acceleration components for the block and the plane and the normal force acting on the ...
0
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3answers
140 views

Forces and acceleration on rotating objects?

Suppose you have an object undergoing uniform circular motion, with force vector pointing towards the center and another force vector tangential. Can it be said that the net force pointing in the ...
2
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2answers
61 views

Work done by frictional force on a sliding block

A block slides across a table horizontally with an initial velocity $V$. The frictional force $F$ brings it to rest after its Centre of Mass covers distance $S$. What is the work done by the ...
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3answers
78 views

On a scale, why does the heavier object go down?

When you balance a pencil on your finger, I have always wondered, "Why does the heavier part go down, and the lighter, up?"
27
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9answers
3k views

Does it take more energy to open a door when applying force close to the hinge?

Assuming an ordinary hinged door (without any springs), would it take more energy to open it when applying force in the middle of the door (point b), rather than at the end of the door (point a), ...
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0answers
36 views

Calculating the 3-dimensional torque on a non-uniform rigidbody given the angular acceleration about its center of mass

Say I have a rigidbody, made up of several point particles with known masses and positions relative to the center of mass. How would I find the torque on this rigidbody given its angular acceleration ...