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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Questioning Einstein's view on gravity [duplicate]

Oke, so my mind is blown by Einsteins view on gravity, at least as far as I understand the basics and principles he based his views on. One of the first things that struck me was that most of his ...
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1answer
24 views

How do you find the tension in the real world? (Given a rope in a pulley system)

I'm well aware of the formula to calculate tension, however, given a real world situation where you have a closed pulley system. How do you measure the force (i.e., tension) required to pull on the ...
3
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4answers
202 views

Why do physics students find vectors so difficult to deal with? [on hold]

When I teach introductory physics to undergraduates, I find that although the classes are frequently split into "algebra-based" and "calculus-based" sections, the most difficult concept for any of ...
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3answers
44 views

Net force of the following? [on hold]

The following objects are attached to one another and have difference force directions: Where is the direction of force? And What is the net force? I'm trying to calculate it using their angles, ...
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1answer
34 views

Can the speed of a vehicle be determined based upon the extent of injuries to a pedestrian?

While driving at night in a Prius, at varying speeds of 5-20 MPH in heavy, stop-and-go traffic on a 4 lane city street, two pedestrians in dark clothing were struck (not in a crosswalk). One died of ...
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2answers
41 views

Another condition of calculating work

Let's imagine that there is a box placed at the corner of a table, and I push it so that my applied force makes an angle of 30° from the table's surface. The box would move and, due to the effect ...
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0answers
17 views

developing a stationary soft crash target [on hold]

I would like to measure the available time delay between the GPS and the mounted accelerometer in a vehicle. I performed some braking tests with the maximum 0.5 [g]. However, I would like to perform ...
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1answer
33 views

Center of mass finding question [on hold]

Find the center of mass the rod in the figure if λ (the mass per unit lenght) varies with $x$ according to $\lambda=dm/dx=\beta x^2$, where $\beta$ is a constant. Sorry for quality of picture. I am ...
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44 views

How fast would a 60 km diameter moon ring rotate to simulate 1 G? [on hold]

After seeing this answer regarding increasing mass for greater weight on the moon, my eyes caught the first comment about centrifuges in science fiction. Naturally, the thought of putting Elysium on ...
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0answers
8 views

maximum dislacement on dumping sistem with FDM [on hold]

A precision grinding machine is supported on an isolator that has a stiffness of 1 MN/m and a viscous damping constant of 1 kNs/m. The floor on which the machine is mounted is subjected to a harmonic ...
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1answer
27 views

Position of Centre of Mass [on hold]

Prove that: $$\vec{R}_{CM} =\frac{\sum_{i=0}^n M_i\times \vec{R}_i}{\sum_{i=0}^n M_i }$$ Where, $\vec{R}_i$ and $M_i$ are the position vector and the mass of $i^{th}$ particle in the system ...
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1answer
25 views

Torque and Moment [on hold]

pole vaulter holding a vaulting pole parallel to the ground. the pole is 5 metres long. vaulter grips pole with right hand 10 cm from the top end of the pole and with his left hand 1 metre from the ...
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3answers
63 views

Why doesn't an object that collides with one that is at rest just do a 180?

Newton's third law says "for every action, there's an equal and opposite reaction." So why is it, say, that when a pool/billiards ball hits the wall of the table, the ball doesn't just turn around?
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1answer
47 views

Two boys pull a rope in the two edges with the force 50 N each. Will the rope rip if it can handle only a pull of 80 N? [on hold]

I think we should make the sum the two forces 50+50=100 N and say it can't handle? Can you explain me using the 3rd Newton Law?
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2answers
38 views

Is it possible to use a magnet to move a steel carriage, which is tied to the magnet? [on hold]

I think yes, but the mass of the carriage is pretty high. Can you answer using the third law of newton?
0
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1answer
39 views

Jumping off a boat vs ship [on hold]

Why it is harder to jump towards the coast in a boat than in a ship (more massive than the boat) that is equally near as the boat? I think we should use Newton Law's and this happens because the mass ...
1
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1answer
41 views

What happens when a force is not applied on the centre of the mass? [duplicate]

The answer to this question force applied not on the center of mass states that for a force applied not directly on the center of mass will have the same linear acceleration as one applied on the ...
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6answers
3k views

Conservation of momentum when rain pours into a wagon

Suppose a wagon is moving at constant velocity on a friction-less surface, and rain begins to fill the wagon. The net force on the wagon is zero, so momentum is conserved; as the mass of the wagon ...
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1answer
43 views

What is the motion of a balloon with a person climbing on a ladder?

Suppose you had a balloon of mass $M$ in the atmosphere at rest relative to the ground, with a ladder attached reaching towards the ground. A person (of mass less than $M$) begins climbing up the ...
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2answers
26 views

Tension of 2 massless springs joined together

A cable is formed by joining two massless springs with different spring constants. Spring A has constant k1. Spring B has constant k2. If mass M1 hangs from the cable, is the tension greater on ...
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1answer
26 views

Understanding tension principles in a 2 pulley system [on hold]

Trying to understand tensions in a 2 pulley rope system, where M1>M2. Is it true that T1>T2>T3?
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4answers
292 views

Why don't we take force proportional to velocity? [duplicate]

When a Force is applied on a body at rest, it produces Acceleration which is equal to change in Velocity. But due to the Force, we see that the Velocity is increasing consequently. So why don't we ...
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1answer
24 views

What forces cause the centripetal acceleration in circular motion on a merry-go-round?

Suppose you stand on a merry-go-round spinning at $f$ revolutions per second and you are $R$ meters from the center. What forces act on you? If you were tied to a rope like in Fig 2 you would follow ...
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4answers
73 views

Newtons third law and unbreakability [on hold]

We all know Newton's third law. But then why this law doesn't work when we place a 1000KG heavy container on a small weak table. The table will break. Pressure is exerted on table by container, and ...
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2answers
53 views

Why is the potential energy for a body raised up by a height negative?

I tried deriving the potential energy of a body when raised at a height $h$ above the earths surface, using the formula: $$PE = -W_\text{conservative}$$ where $W_\text{conservative}$ is the work ...
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0answers
26 views

Determine a gradient field [on hold]

Given the following field of force, $$ \vec F(\vec r) =\begin{pmatrix} 2x+2y+az \\ 2x-3ay \\ 4x+c+2z+yd \\ \end{pmatrix} $$ My exercise is to determine $a,b,c$ ...
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0answers
27 views

Period of a pendulum in a lift going up [duplicate]

So I know that the period of a pendulum in a free falling elevator isn't going to change because there is no force acting on it since $$T = 2\pi\sqrt{\frac{\ell}{g}}.$$ So what happens to a pendulums ...
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2answers
64 views

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
27 views

Period of oscillations for hanging and standing spheres [on hold]

Consider the following case The darker brown half is of a higher density than the lighter brown, and both represent spheres. In figure a, the sphere is somehow suspended in the air (in hindsight ...
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2answers
92 views

Torque and Pulleys [on hold]

I have the solution to the problem below, however I approached the question differently than my professor and I do not understand why my answer is different. Can someone help explain where I'm ...
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0answers
113 views

Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth?

According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 Explosive Space Modulator will require $1.711 \cdot 10^{32}~\text{J}$ to shatter the Earth into a gravitationally ...
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2answers
55 views

Will terminal velocity exist on this imaginary planet?

If the atmosphere of an imaginary planet is really thin like 100 particles per cubic centimeter (density of the closest resemblance of vacuum made on Earth) and has mass say, 15 times than that of ...
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2answers
57 views

Why don't the two forces balance each other In Newton 3rd law? [duplicate]

Why don't the two forces of action and reaction balance each other ? I imagine that although they are opposite forces, they have different points of application. Is this true?
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2answers
907 views

Will a bullet dropped and a bullet fired from a gun horizontally REALLY hit the ground at the same time when air drag is taken into account?

In a world without air, I understand they definitely would. However, with drag taken into account, I think they wouldn't. Since the drag force varies proportional to the square of speed (ignoring the ...
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2answers
48 views

what is difference between homogeneous vs isotropic material?

When we say a material is isotropic? When properties such as density, Young's modulus etc. are same in all directions. If these properties are direction dependent, then we can say that the material is ...
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1answer
40 views

What am i doing wrong here(dynamics)?they should give the same answer [closed]

So a body $m$ is on a uniform circular motion ($\omega = d\theta/dt = \text{constant}$), it is suspended by an inextensible rope with negligeable mass: First picture so: $$ -mg + T \cos \alpha = ...
2
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1answer
28 views

a problem on finding acceleration by differentiation

The displacement of particle along the $x$ and $y$ axis is \begin{cases} x(t)=\omega t-\sin\omega t\\ y(u)=1-\cos\omega t \end{cases} Upon differentiation, the velocity is \begin{cases} ...
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2answers
36 views

Does juggling faster less work then juggling slower?

I got this idea when juggling. Let's say three balls with the standard technique. When I throw the balls higher it is harder (more work), but since it takes more time for them to fall back I work less ...
2
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2answers
71 views

Understanding relationship between work and energy

I've read over 10 books about work and energy, and I just simply can't understand it. First of all, they go ahead and randomly define that work is force times distance: $$W=F X \cos\theta$$ Okay, ...
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2answers
29 views

Computing lengths for a rotating rod

I know how to assign dimensions to a profile that is under static loading - that is under Mechanics of Materials, I would agree on a beam section, calculate the maximum moment and use the elasticity ...
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0answers
16 views

Dynamics particle motion around ellipse [closed]

For particle motion at constant speed around an ellipse with a major axis of 4 inches and a minor axis of 2 inches the ratio of the acceleration at pt. A to B is?
2
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4answers
67 views

What is the intuition behind “Net Work is Zero”?

I tried searching the answer to this all over the internet, but still cannot grasp this concept. So, when a book is being lifted, let's say $25 meters$ with a mass of $4kg$, with constant speed. I ...
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2answers
23 views

Does the effect change if a continuing and constant force acts upon a mass?

If a continuing and constant force $F$ acts upon a body with the mass $m$, does the power (work per unit time) increase over time? It would mean that the converted energy per time unit increases. Is ...
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2answers
59 views

Playing catch in space?

I was thinking about this on the bus (exam this week :P). What would happen if two people played catch in outer space? Lets say person A and B are in space at rest, A throws a mass m at B, what ...
4
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2answers
208 views

Can very large objects have a gravitational moment?

I was reading this answer about center of gravity vs. center of mass and it stated: Consider the Sears Tower. Its CG is about 1 millimeter below its CM. The reason why is because the base of the ...
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1answer
31 views

A sailboat and wind, to find $v(t)$

Consider a sailboat of mass $m$ that lies on still water. A wind blows the sailboat with velocity $v_w$ perpendicular to the sailboat. If the boat has a sail with area $A$, and the air density is ...
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2answers
80 views

Ratio of the magnitude of the normal force to the magnitude of the gravitational force? [closed]

I'm working through some practice problems in preparation for my physics final and ran into one that I'm not sure how to do. A mass is released from rest from the edge of a large hemispherical, ...
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0answers
35 views

Classical Mechanics - Stable Equilibrium and Escape Velocity [closed]

So I've done a previous part of this question which I'll show the information gathered. For a given potential energy function of $V(x) = cx/(x^2 + a^2)$, stable equilibrium was at $x=c/2a^2$ and ...
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1answer
53 views

Classical Mechanics - Potential Energy Function [closed]

Question The potential energy function of a particle of mass $m$ is: $$V(x) = \frac{cx}{x^2+a^2}$$ where c and a are positive constants. Qualitatively sketch $V$ as a function of $x$. Find two ...
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3answers
50 views

Force on a solid cylinder that is rolling on an accelerating block

Given: $m,R,I=mR^2/2, F,M$ and no traction between $B_2$ and the ground find $a_1, a_2$ (the accelerations of the CMs of $B_1$ and $B_2$ respectively).$B_1$ rolls on $B_2$ without sliding due to ...