# Tagged Questions

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.

8 views

### Newton's 3rd law… hitting drywall (which I break) vs hitting a brick (which breaks me)?

For every action there is an equal and reaction. -Third law of motion So, I understand that if I hit a brick wall with 50 lbs of force, the brick wall also hits me with 50 lbs of force (usually ...
27 views

### What causes more damage, a head-on car crash at 30km/h or one car at 60km/h crashing into a stationary one?

Which will cause a greater impact? Two identical cars colliding head on (in opposite directions), each going at 30km/h OR One car travelling at 60km/h colliding into a stationary car (for the ...
113 views

### Sliding blocks problem

My first post here, so I apologize if this is duplicated elsewhere. It IS a "homework" problem, but it's public domain, a posted exam with answers... http://www.mun.ca/physics/undergraduates/...
14 views

### a spring is stretched 10mm by a weight of 2.0N calculate the force constant k [on hold]

stretched 0.01metres weight of 2.0newtons calculate force constant k calculate the weight of an object that causes an extension of 80 millimetres
29 views

### Extinction level meteor effects on Earth's crust pending on the surface area upon impact

Would it be possible to have a extinction level meteor hit Earth depending on shape to actually create minimal damage if turned on its thinnest area rather than hitting flat? The meteor would enter ...
564 views

### Newton's Second Law Confusion

I don't quite understand the relationship between an object's mass, acceleration and net force. For example, if a car was going to the right at a constant velocity or with no acceleration, does that ...
5k views

### What factors affect the velocity of an object moving down an inclined plane?

If you have a small toy car rolling down an wooden plank, what factors would increase or decrease the velocity of said car. In the experiment my team originally stated that adding mass to the car ...
452 views

### Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
51 views

### Use of $g$ for centripetal acceleration

I have attached an image above including the question I'm unsure of (part B) In a nutshell, a satellite is orbiting Earth at the surface. Given is $g$ and the radius of the Earth. For part bi) the ...
636 views

### Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
60 views

### Question regarding elastic collisions and the conservation of momentum / energy [on hold]

I've been working on this question for a few hours and I cannot quite convince myself that my answer is correct. I've read the relevant section in my textbook, but I guess the lightbulb just isn't ...
29 views

### What will be the new moment of inertia? [on hold]

Let assume we have a sphere of radius $R$, and we can simply calculate the moment of inertia if we consider the axis is going through the center O. Let's cut a sphere small radius $r$ from the sphere ...
138 views

### Few questions related to Tension

I am struggling with the concept of tension in a rope. Below specific questions. I am understanding tension to be an elastic force between rope molecules. If so, is it fair to say the net tension ...
138 views

### Is sonic boom louder than the sounds that a object traveling at the speed of sound makes, if so why?

Here are the wave-front models for both: I am in an introductory physics course. Just learned about this. I am not entirely sure if sonic boom is louder. But from what I saw, it's loudness is ...
40 views

### High School Physics [on hold]

Two girls are standing on a bridge over a river. One girl falls freely and the other ties a rope to her legs. Both jump at the same time from the bridge. The length of the rope is more than the ...
59 views

### Why move from Special Relativity to General Relativity? [on hold]

The concept of relativity is simple. Why take Maxwell's equations to a new Special Relativity level with the unproven assumption that photons have no mass? All other physical data (momentum, affected ...
37 views

### basic question about work exercise [on hold]

I am learning independently from Tobochnik's statistical physics text. He asks a warm up question about work: A person pushes a block up a frictionless ramp. Is the work positive, negative, ...
28 views

### Force dependence on velocity : Drag

I just listened to the second lecture of Leonard Susskind on classical mechanics where he discussed that force can't be proportional to velocity, since it's unable to retro-dict (predict past). He ...
1k views

### What is the longest distance that can be jumped after swinging from a rope?

In the movie Mission Impossible 3, the main character Ethan Hunt tries to enter a building in Shanghai by swing through the sky, as shown below: The jump consists of 2 sections, the red part, which ...
19 views

### Analysing kinetic energy in different frames [duplicate]

Case A: Say we observe a body X moving with a velocity of 30 on the +x and we(the observer) are stationary. Case B: The observer moves with a velocity of 50 on the -x. The body X is moving in the ...
280 views

### Rate at which a pendulum bob slows due to air resistance?

I know that "perfect" pendulums would be able to swing forever, unperturbed by air resistance. However, since there is air resistance around us, pendulums (swinging bobs) slow down and move closer and ...
54 views

### Velocity of satellite to crash into the earth

I was reading through this post today and was very impressed by the response that was given. However, what would have to happen to the velocity in order to collide with the Earth? Velocity of ...
40 views

### Does displacement affect force? [on hold]

I am sorry for being unclear with my previous question. The main topic of the experiment we conducted was about work. As we learned: $W = Fd$ Work, from my understanding, is the product of work and ...
435 views

### How do I describe the order of events in spacetime?

In Newtonian mechanics, we have 3-space and time. Time allows us to order events. For example, I hold a ball in the air at time $t_0$. Then I drop it at some later time $t_1 > t_0$. Finally it hits ...
179 views

### Is the double pendulum an example of a strange attractor?

Imagine a pendulum to which is attached another one (not necessarily the same length). Does this pendulum, when you let it go (which can be done in many ways but let's keep the total potential ...
36 views

### What really is force? [duplicate]

I know the second law of Newton says $F=ma$ which seems to me the most fundamental expression of the force. In other words, force cannot exist without a "forced" one. It is somehow a "secondary" being,...
114 views

### Problem in constraint equations

In this, if I want the acceleration constraint between $M$ and $2M$, I write $AM+2AB$=LENGTH OF STRING, which on differentiating twice gives $a_{m}=2a_{2m}$(which turns out to be correct). However, if ...
376 views

### Are Newton's laws followed in non-inertial frame of references having all their objects and observer moving with same acceleration? [on hold]

Consider a hypothetical scenario. In our universe there are two merry-go-rounds 1 and 2 and a distant planet. There is no other object having mass. There is a robot X on the planet. There are two ...
16 views

### Simple harmonic motion [on hold]

A body executing shm has 10cm as amplitude and time period is 1.5s. Calculate the time taken by the body to travel a distance 5√3 cm from the mean position. I have used the formula x=asim(wt) And ...
10k views

### Understanding tension

I'm trying to understand tension. So here it goes: I'll start from the beginning. Let's assume I'm in space and can move around and apply forces. Let's say a rope is attached to a body(which is in ...
47 views

### Work done by internal forces of a rigid body

I am reading Goldstein's Classical Mechanics book, and I came across that: In a rigid body the internal forces do no work Is this statement based on the assumption that the internal forces are ...
291 views

### Centripetal and centrifugal force

If a stone is rotated with the help of a rope, then both centripetal force and centrifugal force will be liberated. The magnitude of that forces are same, but direction of them are opposite to each ...
5k views

### Uniform chain falls off table Diff EQ

I really need some assistance setting up this problem. any assistance would be a Godsend: a uniform heavy chain of length a initially has length ...
331 views

### Derivation of Universal Variables

Does anyone know of link to the derivation of the Universal Variables? This is in regards to Kepler's equations. The Wikipedia link didn't have enough information for me, and the Colorado page doesn'...
102 views

### Why do icebergs move perpendicular to the wind?

I know it has to do with to Coriolis force and the Ekman layer but I didn't really understand the explanation. From Wikipedia: "Ekman transport, part of Ekman motion theory first investigated in ...
24 views

### Stuck with 2D kinetics problem [on hold]

I've been trying to solve this exercise for the last four hours and I'm totally stuck. The problems goes like this: Given the mechanism in the image, located in the vertical plane, the OB cord ...
11 views

### How do rockets fly? [duplicate]

Is it that when a rocket loses its mass due to the escaping gases that results in its acceleration due to the same force acting upwards? If so, how is Newton's Third Law associated with it?
32 views

### Forces on body above body moving at constant velocity [on hold]

Let's say the system is moving at constant velocity. What are the forces applied on B? Is there a static friction force? I find it hard to imagine what is happening to object B. $\Sigma F$ is $0$ on A ...
45 views

### How do gravitational sling shots work? [duplicate]

How can an object move faster after leaving the gravity of a planet, should a gain in potential energy by moving away from the planet lead to a loss of kinetic energy? Or am I missing something ...
1k views

### Why is Newton's first law necessary?

Newton's second law says $F=ma$. Now if we put $F=0$ we get $a=0$ which is Newton's first law. So why do we need Newton's first law ? Before asking I did some searching and I got this: Newtons first ...
56 views

### Conservation of enegry in case of Exploding Projectile [closed]

Consider the following problem : A projectile of mass M explodes, while in flight, into three fragments. One fragment of mass $m_1 =\frac12 M$ travels in the original direction of the projectile. ...
142 views

### Why is the object's maximum speed at $x=0$ for spring? [on hold]

My book derives velocity of the hanging object of a horizontal spring (on frictionless surface) as a function position: $$v=\pm \sqrt{\frac{k}{m}(A^2-x^2)}$$ and shows the maximum speed is at when x (...
159 views

### Normal Force in Circular Motion

In the above diagram, sec 1 (on the left side), an object of mass $m$, after releasing from rest from a slant track, continues into a vertical circular track. At a random position on the circular ...
40 views

### Friction and movement in a system with body above moving body in newtonian mechanics [closed]

I have a problem in analyzing movement with friction involved. I do not know how to correctly analyze systems as such and what is the correct view. I have tried to answer the several question below. ...
36 views

### understanding kinetic friction [on hold]

I have a pen on my table. I apply force horizontally to my pen. The force I apply is stronger then the maximum static friction so it moves. I move the pen at constant velocity. Now if we look ...
240 views

### Torsional spring and Euler angles

I have a question about the moments generated by torsional springs. Consider an inertial reference frame A and a body fixed reference frame B. The frames are connected by 3 rotational springs acting ...
46 views

### In the following problem, where did $v_{cm}$ come from? [closed]

In the following problem, where did come from? I don't recall any formula that this equation could be derived from...?
170 views

### How can one conclude upward force is related to tension in this question?

In preparation for the SAT Physics Subject Test, I have been doing extra practice problems. This one states: A garment bag hangs from a clothesline. The tension in the clothesline is $10 \,\text{N}$ ...
I understand that the Riemann Invariants for an expansion wave (isentropic) are constant along the particular characteristic line i.e.: $u + \frac{2c}{\gamma-1} = const$ along $dx/dt=u+a$ (1) ...