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.

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2answers
29 views

What is a CCD structure?

In a exam paper for entry into Oxford University for physics, I came accross something which I hadn't met before, and I have no idea what the question is asking - none of my teachers could explain it ...
-2
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1answer
21 views

Question on kinetic energy, mass and velocity [on hold]

Two bodies have kinetic energies in the ratio of 4:1 They are moving with equal linear momentum. What is the ratio of their masses. My answer : I get $$\frac{m_1}{m_2}=\frac{4v^{2}_2}{v^{2}_1}$$
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1answer
23 views

Power - 1/2 Force x velocity? [on hold]

A pump, taking water from a large reservoir, is used to spray a jet of water with speed 20m/s. The nozzle of the pipe has radius 0.05m, and is level with the surface of the reservoir (no change in ...
2
votes
2answers
74 views

What is the cause of planetary rotation. Not orbital rotation [on hold]

I am a senior in high school, sixteen years old. I think differently than most in my class. Recently, I have been thinking about alternative causes for the rotation of our planets. My current thought ...
0
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2answers
43 views

Nondimensionalization of a simple system [on hold]

A damped spring mass system is modelled below: $$m\frac{d^2y}{dt^2}=F_s+F_d\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space t>0$$ ...
11
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2answers
2k views

Why are a motorcycle's front brakes more effective than back?

I've noticed that when I apply the front brakes on my bike it stops quite quickly. If I apply the back brakes at the same speed, it skids rather than stopping quickly. Why?
1
vote
1answer
79 views

Can there be force without motion?

I am confused. Can you have a force or tension without motion? Take for instance two robots with jet packs connected via a cord, each is flying in opposite directions. The tension of the cord is ...
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0answers
18 views

Forces at each point for a simple truss [on hold]

I have a truss here: It is given that the forces at point 2 are horizontally and vertically. Positive values for lowercase f forces indicate tension, and negative ones indicate compression. I ...
1
vote
1answer
32 views

Work done in case of an accelerating object [on hold]

How do you calculate work when opposing force is less than applied force. So a 5 N static friction force is overcome by 15 N manual force for say 5 meter. What is the work done by manual force?
-1
votes
0answers
18 views

Physics question dealing with friction and something else [on hold]

I have 2 questions A 10 kg block is placed on top of a 20 kg block. The top block is then pulled toward the right with a force of 60 n. IF the coefficient of f kinetic friction bewtween the floor ...
0
votes
1answer
57 views

Is this expression for the kinetic energy of a spinning disk revolving about a second axis correct?

My question is motivated from a question from another user. You can see the configuration of the rotating system here: One disk/ring in double rotation and sum of energy. I am not interested in all ...
2
votes
2answers
28 views

Bungee jumping - find spring constant

A person of mass $m$ is attached to a spring that its loose length is $l_0$. He is standing on a bridge and jumps off it, so he travels down a distance $2 l_0$ when measured from the bridge up to the ...
0
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2answers
48 views

What is the jerk due to gravity with ascent? [on hold]

Acceleration is defined as the rate of change of velocity with time. Jerk is defined as the rate of change of acceleration with time. What is the jerk due to gravity with ascent?
-4
votes
1answer
33 views

Mechanics, work, spring [on hold]

I'm off by a factor of 2 according to the solutions, but I can't see why. Question: A force of 800N stretches a (weightless, horizontal) spring by a distance of 0.200m. What is the potential ...
2
votes
2answers
35 views

Is the coefficient of restitution frame independent and energy conservation?

In this question I am ignoring relativistic effects. The following statements I think are true: change in Kinetic energy is not invariant under change of frame Force is invariant under change in ...
-2
votes
0answers
30 views

Two masses attached by a spring (differential equation) [on hold]

Consider two masses $m_1$ and $m_2$, connected by a spring of spring constant $k$ and an uncompressed length $L$. The masses are on a frictionless surface. Initially, $m_2$ compresses the spring to $L ...
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vote
2answers
66 views

Does a ball spin more from left to right than it does from right to left?

I swear that in a manual on tennis published by the German Tennis Association (Deutscher Tennis Bund) it stated as fact that all things being equal a ball will move more from left to right than from ...
2
votes
1answer
83 views

Does an externally driven Foucault pendulum really demonstrate the rotation of the Earth?

There's a Foucault pendulum at my school. It's a 105 kg ball suspended from the ceiling with a 20.73 m wire (source in French). There seems to be a driving mechanism on top, where the wire is ...
0
votes
1answer
32 views

Is the moment of zero velocity identical for objects of differing mass?

Assume we have two perfect spheres of identical size but different mass (e.g., one made of steel and one made of enamel) and an environment where the only forces in play are gravity and velocity ...
0
votes
3answers
71 views

In this pulley system, if the mass was on the table greater than the handing mass, would tension equal Fg of the hanging mass? [on hold]

If the mass on the table was greater than the hanging mass, would the the tension force equal the force of gravity on the hanging mass?
0
votes
1answer
19 views

Friction and Conservation of Angular Momentum [on hold]

suppose we have 2 discs placed on a smooth horizontal surface.... one of the discs say A is rotating with W angular velocity and is slowly brought near the other disc kept fixed about its centre but ...
0
votes
0answers
38 views

Asymmetrical Newton's Cradle [on hold]

If we have a Newtons Cradle with decreasing ball size how do the small ones behave when hit by the larger ones? Do more balls move with the same velocity, or do a smaller number of balls move with a ...
0
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0answers
33 views

Derivation of wave-velocity from a wave-equation [on hold]

I am asking for a derivation of the wave-velocity $c$ in terms of the compression modulus $K$ and the density $\rho$. The basis for the derivation should be the acoustic 2-way wave-equation in a ...
2
votes
1answer
26 views

Conservation of energy and inclines

I have question which I'm unsure of whether or not I am thinking about it right. If an object is sliding down frictionless incline and it then comes to the "foot" of the incline where it encounters ...
1
vote
1answer
41 views

Superfluid rotating frame of reference

I'm currently studying a text about Bose-Einstein condensates (BECs) and vortices. When they want to study whether a vortex will be formed, they look at the fact wether it's enegetically favorable. ...
0
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0answers
43 views

Newtonian gravity in 3D space, with 2 point masses, calculus, no approximations [on hold]

I have been trying to find this information all over the net and can't find a straight answer. Here is what I am looking for. How do I take Newton's law of gravity to get final position, velocity, ...
-1
votes
0answers
9 views

application of out a moment of force about a line [on hold]

give a practical example of r x F.a cap, which is a moment of force about a line. This question is on triple product. I would like to know an engineering example for moment about a line but about a ...
-1
votes
1answer
27 views

Explain the terminal velocity equation [on hold]

As explained by Method 1 on WikiHow, the equation for Terminal Velocity is: $$ V_T = \sqrt{2 \times m \times g \over ρ \times A \times C} $$ Some parts of this equation are self explanatory, and ...
0
votes
1answer
53 views

Changing momentum of moving trolley

We have a trolley of mass $m$ and it is moving at a velocity $v$ along a smooth horizontal plane. It is full of water, and is leaking water at a constant rate out of the bottom of the trolley, i.e ...
0
votes
1answer
55 views

Newton's Third Law Intuition Help

The problem states the following: A 1,000 Kg car pushes a 2,000 Kg truck that has a dead battery. When the driver steps on the accelerator, the drive wheels of the car push against the ground with a ...
-10
votes
0answers
74 views

Deriving Newton's Second Law [on hold]

How do I derive μ = Tan[θ] ? Step by step instructions please.
0
votes
0answers
52 views

why ostriches cannot fly? physics explanation

I'm looking for a physics explanation concerning to the fact "The ostriches cannot fly". My statments: During the time interval $\Delta$t of the upward wingbeat, the ostrich drops a distance h ...
0
votes
1answer
47 views

Rotational Inertia of Two rods [on hold]

In the figure, two particles, each with mass $ = 0.82 \text { kg}$ are fastened to each other, and to a rotation axis at $O$, by two thin rods, each with length $d = 5.3 \text { cm}$ and mass $M = 1.0 ...
1
vote
3answers
343 views

Is Newton's third law universal, does it apply to momentum or also to forces?

I read all the previous answers concerning the 3rd law and I have seen that it is definitely not universal, (Edit: but conservation of momentum is. If it is not universal it should be not a problem to ...
0
votes
1answer
48 views

Gravitation Field inside hollow sphere [closed]

for this homework problem I am trying to work out the gravitation field inside a hollow sphere. I have searched for a while now and haven't found a good post working it out thoroughly. One thing I ...
14
votes
5answers
4k views

How fast would someone have to run to travel vertically up a wall? [on hold]

I am currently doing a physics project on the effects of so-called 'super-speed'.I was wondering how fast you would have to run to vertically travel up a wall? That is, to negate the force of gravity. ...
4
votes
2answers
493 views

Does a force act on the body during collision

Consider two bodies A(black) and B(red) having equal mass. A is moving at a constant speed towards B, which is stationary. At certain point of time, they collide elastically, $\therefore u_{A}=v_{B}$ ...
3
votes
2answers
155 views

Water escaping from a pendulum bob, how is time period affected? [closed]

well the question is: A hollow pendulum Bob filled with water has a small hole at bottom, through which water escapes at a constant rate. How is the time period(T) affected as the water flows out? I ...
2
votes
1answer
45 views

Confused about gravitational potential energy [duplicate]

So learning the concept of gravitational potential energy, my professor says that when lifting an object without any acceleration, the force we exert on the object to lift it is the same as the force ...
4
votes
3answers
171 views

Why is $\pi$ used when calculating the value of $g$ in pendulum motion?

I am trying to intuitively understand why $\pi$ is used when calculating the value of $g$ using the harmonic motion of a pendulum: $$g ~=~\frac{4\pi^2L}{T^2}.$$ Does it have something to do with the ...
0
votes
0answers
26 views

Finding most/least tension between 5 cars attached to a train [closed]

I am currently doing Grade 11 physics and I have been troubled by this one question for homework for quite a while. Hopefully most of you will be able to help me out. Question: A 40,000kg train ...
1
vote
0answers
22 views

Recommend books on mechanics, motion and it's laws [duplicate]

I want a book that discuss all these things practically. I don't require it for any exam. Just for applying it confidently anywhere (want to Analyse fluids,thermo etc.) Want a book that explain how to ...
2
votes
1answer
29 views

Separating the potential energy of a system of particles.

Assuming all forces derive form a conservative source and that all forces observe the strong form of the third law, how do we arrive at the following equation? \begin{equation} V=\sum _i V_i+\frac ...
0
votes
0answers
18 views

A box up an inclined ramp with a coefficient of friction [closed]

A 6.25 horsepower motor to pull the boxes a distance of 8.35 meters up a ramp inclined at an angle of 36.2º with respect to horizontal. The boxes have a coefficient of kinetic friction of 0.381 as ...
1
vote
2answers
61 views

Is a double integral required to find the moment of Inertia of a non-uniform sphere?

Consider some ball of given radius $R$, with a mass density function that depends on the radial variable, $\rho=\rho(r)$ where $r$ is the distance from the center of the sphere. What is the moment ...
3
votes
3answers
55 views

what make the bottom portion of a wheel in rolling motion move?

As I just learn about the rolling motion which is the combination of pure translation and pure rotation. The top portion of the rolling body has the speed of double speed at the center of the object ...
-2
votes
1answer
32 views

What causes the recessed blade of some folding knives to emerge in a kinetic opening? [closed]

KINETIC OPENING OF FOLDING KNIFE (FK) Several legal jurisdictions around the World, including Australia, have assented legislation/regulation which attribute the emergence of the recessed blade in the ...
0
votes
0answers
18 views

Role of the crystallographic point group on properties of tensorial elasticity

If a space point group for a crystal is known, does this automatically define the elastic tensor symmetry of the material? What further implications can be found? The crystallographic subgroups: ...
1
vote
1answer
41 views

Hooks Law and acceleration [closed]

A 435 gram sharpened piece of iron rebar into a spring loaded device. It takes a force of 355 Newtons to compress the spring by 27.5 cm. With what speed does the rebar shoot out of the device? ...
-4
votes
0answers
18 views

Law of conservation of linear momentum is a consequence of Newton's forst law substantiate [closed]

Law of conservation of linear momentum is a consequence of Newton's first law substantiate.