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.

learn more… | top users | synonyms (3)

2
votes
3answers
100 views

Armageddon prevention

I was watching the movie Armageddon and it made me think of a few things. We would probably not need to send a crew to blow the asteroid in two, I think we could still send a warhead with enough power ...
1
vote
1answer
70 views

When is momentum not conserved?

What are some common examples where momentum is not conserved? This question arose in my mind when I read that a ball dropped from a height penetrates into a bed of sand and that momentum is ...
0
votes
1answer
20 views

Two-block system acceleration when applying a force in the $x$ direction

Two blocks are connected by a light-weight string that passes over a friction-less pulley (a.k.a. Atwood's machine). Block # 1 (called $m_1$) hangs from the edge of a friction-less table. Block # 2 ...
2
votes
2answers
109 views

“Magic” Speed to Drive Over a Speed Bump: Myth or Reality?

A somewhat controversial point about speed bumps (sleeping policemen for those in the UK) is that they arguably cause more loss of life than they prevent by acting as a hindrance to emergency response ...
1
vote
1answer
30 views

Spring Powered Car - Which Design Is Best? [on hold]

I'm in the preliminary stages of building a spring powered car to race over a distance of 10 metres. It is a yearly event held in my local area and so far we've only seen one spring powered car. I ...
28
votes
10answers
2k views

Where does the extra force generated by a lever come from?

Given an object being pulled down to earth by a force of 1000 lb: If a machine were to lift it off the ground for me, and I grabbed on to the rope before it was released, there is no way in the world ...
3
votes
1answer
39 views

Calculating time to reach certain velocity with drag force

I was given a problem for homework where we needed to calculate the time for a falling object to reach a certain velocity when accounting for drag force. I did it by setting up acceleration as a ...
1
vote
1answer
201 views

Does a heavy body move with the slightest force on a frictionless surface?

If I apply horizontal force on a body resting on the ground, my force will be opposed by the frictional force and the body will accelerate at the point where my force exceeds the force of friction = ...
0
votes
2answers
63 views

Can you punch a hole in an A4 sheet of paper with your hand?

The Heading says it all. But let me explain it a little further. Suppose you hang a sheet of paper (A4 size), from one end leaving the other end free. Now practically it seems impossible to punch a ...
1
vote
2answers
20 views

Possiblity of predicting behavior of system when properties described as functions over space?

Suppose I am given a system that consists of a distribution of charged particles(which are all over space and are point-charges). They are described by a set of functions instead of variables. These ...
1
vote
2answers
64 views

Finding sphere of influence in multibody system

I would like to draw a boundary illustrating the sphere of influence of each body in a 3 body system. What is the best way to find such a boundary? My understanding is at the edge an SoI is the ...
1
vote
2answers
88 views

What causes a tall box to tip over on an inclined plane?

I'm wondering what makes a tall box rotate about its edge (the red point on the figure below) on a inclined plane (with or without slipping), when subjected to forces of gravity and friction only: ...
0
votes
0answers
27 views

Where is the maximum center of mass so it doesn't fall over? [on hold]

I have some sort of barrow with brakes, which its deceleration due to the braking never makes the crate slide down: I have found it is $\mathbf{a} \leq g(\mu\cos\theta - \sin\theta)$ (note that it ...
0
votes
2answers
41 views

Is centrifugal force equal in magnitude to the centripetal force in the frame of a body undergoing circular motion?

I was working out the minimum tangential velocity required for a swing to complete a full revolution and assumed the centripetal force is equal to the centrifugal force, so that I could set the weight ...
1
vote
2answers
94 views

Add weight in front or behind the moving wheel?

Consider a wheel with bearing and axle bar rolling on level ground. If I want to help the wheel continue moving longer(or faster speed), should I add weight by moving the rider body in front or ...
1
vote
0answers
34 views

How torque and friction cause wheel to roll

I apologize if this question has been answered before, but I did not find the explanation that I needed. If a torque is applied to a wheel situated on a frictional surface, what forces cause the ...
2
votes
2answers
68 views

Deceleration rate of objects of different mass but the same otherwise

Using a tennis ball as an example object, if one ball weighs 1 ounce and the other is 2 ounces, and both are struck at 100 mph on the same trajectory, would there be any difference in the deceleration ...
1
vote
0answers
44 views

Tension Problem: Solve for T for two sliding blocks connected by a string [on hold]

The problem: Two blocks made of different materials connected together by a thin cord, slide down a plane ramp inclined at an angle θ to the horizontal as shown in the figure (block B is above ...
5
votes
1answer
151 views

Giant leap of the space goat

This problem was inspired by this Math.SE post and similar problems involving tethered animals. A space goat is tethered to the north pole of a spherical asteroid of uniform density and radius $a$ ...
1
vote
1answer
40 views

Static and kinetic friction [on hold]

Say you have block1 on top of block 2 and the whole system is accelerating toward the right at a certain acceleration. Due to inertia block 1 wants to move backward to the left so there has to be a ...
1
vote
1answer
32 views

General potential of rotating system

I'm new here at the physics site, and not really that deep into the area of which i'm going to ask a question about now. Therefore please feel free to ask clarifying questions. I'm trying to deal ...
5
votes
5answers
88 views

Forces while squeezing a toothpaste tube

When I squeeze a tube of toothpaste, I am working with 2 squeeze forces toward tube. What causes the toothpaste to go out of the tube? (instead of remaining stationary)
6
votes
1answer
49 views

Movement of a cylinder filled with water

Not long ago I was pretty bored at a dinner and I started playing with a water bottle that was not empty: I've been quite interested in its behavior when putted on its side and pushed: the bottle of ...
0
votes
0answers
49 views

Electromagnet force equation clarification

So, from a previous previous question, I know what plane the force from an electromagnet will affect a ferromagnetic material in. I thought that would be enough, but working through some problems ...
1
vote
2answers
29 views

Diagram of forces exerted on objects

Assuming that there is an interaction between 1 and 3 (they attract each other), what are the forces between 1 and 2? I know it is as if the force acts on a different body (1+2), but I want to know ...
4
votes
3answers
103 views

How to calculate when wheels are better than legs?

We all know that it uses less energy to go by wheeled transport than walking if the terrain is smooth and there are not too many hills. We also all know that when going up steep hills we get off ...
1
vote
2answers
116 views

If an asteroid were threatening the Earth, could I deviate it just by jumping on it?

An impact by a 10 kilometres asteroid on the Earth has historically caused an extinction-level event due to catastrophic damage to the biosphere. There is also the threat from comets coming ...
5
votes
2answers
113 views

Pulling apart two interleaved phone books

The TV show Mythbusters had an episode in which they interleaved two phone books and dramatized how hard it was to pull them apart. (A long time ago, a phone book was a book that had an index of phone ...
0
votes
1answer
106 views

Can a ball stay still while laying on a inclined plane?

Suppose there is a ball on an inclined plane. So, there are three forces acting on it: normal force from the plane, gravity (which can be decomposed in the component of gravity perpendicular to the ...
3
votes
2answers
72 views

Why are some forces not included in the sum of forces?

I was given the following notes in class: 4.32 A skier of mass $65.0\text{ kg}$ is pulled up a snow-covered slope at constant speed by a tow rope that is parallel to the ground. The ground ...
2
votes
3answers
90 views

Elastic collision of point particle and rod

A 1 meter long rod on the ice with mass $m_2=1$ kg is perpendicularly hit on one end by a point particle with mass $m_1=0.1$ kg. The collision is elastic and the point particle is bounced back in ...
0
votes
0answers
23 views

Effect of an asymmetric weight distribution on a hack squat machine

In a hack squat machine (see figure above), does it matter if I put more washers on one side? May this asymmetry cause an asymmetry of my effort in performing this exercise? For example, if I put ...
1
vote
1answer
20 views

Calculate coefficient of friction from deceleration with and without conservation of energy

How can I solve the following problem? A block that moves at the speed of 120 cm / s keep going for 70 cm before stopping. What's the coefficient of friction between block and table calculated ...
0
votes
2answers
89 views

Why isn't work relative?

Acceleration and displacement can be defined relative inertial frames. For example, a body moving with constant velocity on top of another moving with the same velocity will have zero displacement ...
0
votes
0answers
19 views

Linear slider motor mount location [on hold]

I'm currently designing a linear camera slider, that will be used to hold camera equipment weighing just about 15 Kgs including all of the lenses and monitors and everything else. For those who ...
0
votes
1answer
33 views

Reflection - reaction force direction

Let's say object hits a wall. When the object is reflected does the direction of the reaction force caused on the wall looks like the red arrow ? Does that direction depends on how "strong" object is ...
-2
votes
0answers
14 views

Calculate the maximum displacement of mass 'm' body, when the system is released from rest at euqilibrium? [on hold]

Image Describes about a system at equilibrium, which consists of springs, pulley, and a body of mass 'm'.
1
vote
2answers
92 views

Vertical Circular Motion

I know that I can use conservation of energy to find the velocity of a particle at a point when it's travelling in a vertical circle by saying $$mgr(1-\cos{\theta})=\frac{1}{2}mv^2$$ then ...
1
vote
1answer
45 views

Modeling a stool with three legs pushed on one leg

If a stool with three legs is pushed (horizontally) on one leg in the direction of the axis passing through the other two legs, it starts both moving and rotating. Is it correct to assume 1/3 of ...
1
vote
3answers
141 views

Spontaneous motion in a wind tunnel

Suppose that a hollow truncated cone is placed in a wind tunnel with a steady wind speed $V$. The cone is placed in such a way that it's base of area $A_1$ faces the wind (rather than the other side ...
60
votes
5answers
6k views

Where does the extra kinetic energy come from in a gravitational slingshot?

I read in this answer in this site that the KE a free-falling ball acquires is not originated by the attracting body but that energy was actually stored in the ball when it had been lifted to the ...
2
votes
1answer
58 views

How to calculate wasted energy

Suppose you are pulling a weight along a track at an angle (in the picture 45°). If the object is dislocated by a distance $D_{45}$ let's assume that the mechanical work done on/energy transmitted to ...
0
votes
1answer
26 views

Horizontal distance covered by an object from an initial height to the ground

We are given: An angle $\theta$ with respect to the ground, its initial height $h_0$ and the final distance $d$. How can we find the initial velocity from this information? I tried a bunch of things, ...
0
votes
0answers
21 views

Restricted three body problem

I have the restricted three body problem, which corresponds, to the equation $ \ddot a-2\dot b -a= \displaystyle\frac{\partial U}{\partial a} $ $ \ddot b +2 \dot a-b = \displaystyle\frac{\partial ...
0
votes
0answers
17 views

Action and Reaction on two bodies [duplicate]

If the action and reaction are both equal and opposite then why a body would move? The force exerted by me on the body must be counterbalanced by the force exerted by the body on me.
4
votes
6answers
750 views

Why does the Earth rotate? [duplicate]

Possible Duplicate: Why does every thing spin? So why would the Earth, or any planet for that matter, rotate along an axis? I know of no force which could come into play here, so i assume ...
1
vote
2answers
62 views

Time derivative of angular velocity in rotating reference frame

I am going through a section in a textbook regarding the Newton Euler equations for a system of rigid bodies (robotics text). There is a particular line in the derivation I don't understand, I've ...
1
vote
2answers
141 views

Describing a motion of gyroscope with gimbal

Can you tell be how to set the equations to describe the motion of this machine in movie "Contact": https://www.youtube.com/watch?v=TSaO9VGjLXc This is gyroscope with gimbal, am I right?
3
votes
1answer
86 views

Could $\int (\ddot\phi + \mu\dot\phi^2)d\phi$ ever be negative? How to show it?

I am working on the following problem: Given a mass $m$ at rest at the base of an incline surface shaped like 1/12th of a circle with radius $R$. The mass is pulled up the incline by a rope that ...
0
votes
0answers
44 views

Projectile under quadratic air resistance force

So here's the problem background: A projectile of mass m is shot straight up with initial velocity $v_0$ and feels a quadratic air resistance force of the form $F = −kv^2$, where $k ≡ mg/u^2$. ($k$ ...