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)

0
votes
2answers
208 views

Can you take the integral of $ d^2x\over dt^2$? [closed]

I am messing around with physics problems, and as silly as this maybe how do you take the integral of $$\int_0^\infty xd^2x$$ For example taking Newton's Second law $F=ma$ $$ F=m{d^2x\over dt^2} $$...
1
vote
3answers
51 views

The formula for the kinetic friction on inclined surface

I'm confused about the formula for the force of friction on inclined surface. It says that $f$ (force of friction) = $\mu N$ (where $\mu$ is the coefficient of the friction). Is: $$f = mg\cos(a)\...
1
vote
1answer
80 views

Characteristics of a tight string

There was a question which I came across in newtons law of motion chapter in the physics book by H.C.Verma which was based upon simple atwood machine (atwood machine consists of two unequal masses ...
0
votes
1answer
40 views

Non-linear pendulum (Whittaker's treatise on analytical dynamics of particles)

Reading through Whittaker's "treatise on the analytical dynamics of particles and rigid bodies" I have a question regarding his analysis of the simple nonlinear pendulum at chapter IV. At some point ...
11
votes
5answers
4k views

How does Newton's third law apply to an object interacting with air?

We all know that if I punch the wall with $100\,\mathrm{N}$ force, the wall pushes me back with with $100\,\mathrm{N}$ and I get hurt. But if I punch air with $100\,\mathrm{N}$, does air punches me ...
0
votes
2answers
96 views

Spinning an object in vertical circle

The situation : A block of mass $M$ is tied to a string and is spun around in a vertical circle. The question asks me to calculate the tension in the string 'at the lowest point' after giving ...
2
votes
2answers
304 views

Throwing an object with air resistance

say I were to throw a 1 kg ball vertically upwards 100 m/s, with g=10 and also air resistance $0.01v^2$ . By considering the forces I can determine that the speed at which it lands is less than the ...
0
votes
0answers
32 views

Clarify throwing an object [closed]

Say I were to throw a 1 kg ball vertically upwards 100 m/s, with g=10 and also air resistance $0.01v^2$. By considering the forces I can determine that the speed at which it lands is less than the ...
1
vote
1answer
74 views

roller coaster with weight requirement for a car

My kids went on a roller coaster type ride on the weekend. The staff loading individual (separate) cars on the ride said each had a minimum and maximum requirement to clear a hill - too little, it ...
0
votes
1answer
65 views

push up weight distribution [closed]

I'm about 84 Kg, in push up position (hands on the scales) the scales show about 54 Kg. Can anyone explain briefly the physics of the weight distribution? (I did high school physics decades ago - can'...
0
votes
0answers
22 views

Polygon with moving/rotating vertices (or chained line segments)

Suppose we have a polygon, where vertices are point masses, and rods joining them are massless. Now, we pull one of the vertices, what equations govern the motion. How about if instead of a polygon we ...
0
votes
3answers
55 views

Will the normal force will be different if there is different area of contact?

Let us say 2 soild frustum of height h and having different radius $r_1$ and $r_2$ respectively where $r_1\>> r_2$ having mass same. There is one one frustum which is kept on ground vertically ...
1
vote
1answer
38 views

Homework help: Finding the min speed for the normal to be zero [closed]

PROBLEM: The pipe AB of length L is moving at a constant speed $v$. Find the min speed that is needed so that point $B$'s normal force is zero $N_B = 0$ The solution starts with: $\bf{a}$$_b = \...
0
votes
5answers
108 views

Is acceleration causing displacement or velocity?

When an object is not moving and we affected it by some force does the given velocity cause the motion or is the motion caused by the acceleration? Let us say that we have an object that is not ...
9
votes
5answers
3k views

Will the box move?

Here is a man in a box with wheels on a frictionless surface. Case 1 - The person constantly pushes the box while standing near its wall. Why doesn’t it move? (I know it is because of the 3rd law, ...
0
votes
1answer
170 views

Why does mass not matter on how quickly an object falls? [duplicate]

I've seen all the mathematical proofs and physics demonstrations in vacuums. However, for example, if a hammer falls to the Earth it falls very quickly. But, it can be interpreted another way. The ...
2
votes
2answers
71 views

Why is Work not equal to 625 Joules in this case? [closed]

A variable force $\vec{F} = 3x^2y \vec{i}$ (unit vector) is acting on an object that travels on a square loop in a clockwise direction starting from the origin to (0,5) then (5,5) then (5,0) then back ...
7
votes
1answer
317 views

Intuitive Explanation of Tippe Top Effect?

A friend showed me a tippe top (a special kind of spinning top) lately and asked me about the physics behind it. I thought about it for a while but cannot quite figure it out. So I will throw the ...
4
votes
3answers
2k views

Where does the energy go in a rocket when no work is done?

While playing Kerbal Space Program, I wondered where my chemical energy would go when fired at 90° to the motion. It would do no work on the rocket, but all that energy has to go somewhere, right? ...
0
votes
1answer
87 views

Law of inertia, Frames of reference

Ok, we all know that an Inertial frame of reference is defined like this: "An inertial frame of reference is one frame where Newton's First Law holds, therefore, a body has a constant velocity or ...
-1
votes
1answer
85 views

Work done by gravitational force!

Suppose a ball is $10m$ high from the ground. It will have $E_p = 10mg$. Now, if the ball falls freely then we know $E_k$ will be $0.5mv^2 = E_p$. But it is said that the work done by a force will ...
2
votes
1answer
79 views

Why can we model a body to have a center of mass?

I accept that bodies have a center of mass. I also accept that if I were to suspend a body by only supporting it at its center of mass, then the body wouldn't rotate. In the scenario that we suspend a ...
1
vote
2answers
52 views

Simultaneous: static friction and acceleration

I need help thinking about two events happening simultaneously. I have a heavy block on a surface with static and kinetic coefficients of friction, though they are unknown. The block is connected to ...
-1
votes
1answer
57 views

Change in F vs x graph if spring is torn in half? [duplicate]

The force required to stretch a spring varies with the distance as shown in the figure. If the experiment is performed with the above spring of half the length, the line OA will: (a) shift toward F-...
0
votes
2answers
55 views

Throwing a Ball from the ground

We know that the Potential Energy is equal to Kinect Energy for any object Thrown from the ground. Not in a straight way of the words. But in the a especific case when I use my my arms to throw a ...
-1
votes
1answer
250 views

Rocket projectile motion problem [closed]

I'm not really sure where to start with this question: In a brisk wind from the south-east of $14.1\:\mathrm{m/s}$ a rocket pointed due north is launched from a cliff that is $500\:\mathrm{m}$ above ...
1
vote
2answers
1k views

Instantaneous Centre of Rotation

Let's say a body is undergoing both rotational and translational motion. I know that ICR of the body as a whole will be the point about which the body is doing pure rotation, so basically will be the ...
0
votes
2answers
54 views

Why can we find forces like this using energy methods?

Often to calculate forces in complex situations (usually involving complicated mathematics), I have seen various people employ energy methods. The answer comes out correct, but I can't understand why ...
0
votes
2answers
169 views

Terminal velocity of a sky-diver [closed]

A $75~\text{kg}$ skydiver can be modelled as a rectangular "box," with dimensions $20~\text{cm} \times 40~\text{cm} \times 180~\text{cm}.$ Given the conditions we may use $F_\text{drag}= {1\over 4}...
2
votes
3answers
303 views

Why are triangles drawn like so when working with gravity on an inclined plane?

This is my first year as a physics student, and I've never learned about vectors past a basic level, so this is confusing me. When we have gravity on an inclined plane, we separate it into two ...
3
votes
4answers
345 views

Can infinite work be done?

Wikipedia defines work as follows. In physics, a force is said to do work if, when acting on a body, there is a displacement of the point of application in the direction of the force. Also work ...
0
votes
2answers
42 views

Frames of Reference in a Rotational System

Imagine two concentric rings with different diameters. One is spinning within the other. There is a small gap between the outer diameter of the inner ring and the inner diameter of outer ring. From ...
0
votes
1answer
35 views

Expansion in differential equation (rapid oscillating field) [closed]

Can anyone explain me how to derive the equation in (30.4)? I don't understand what approximations or substitutions are exactly performed.
0
votes
1answer
76 views

Why does $v^2=cad$ by dimensional analysis rather than $v^2=ad$? [closed]

Constants are generally added in functions to adjust for when magnitudes don't contain information necessary to the accuracy of the equation. Why is it that $v^2=cad$ instead of $v^2=ad$? What ...
1
vote
1answer
73 views

A teaser on center of mass of right circular cone?

How can a distinction be made between the centre of mass of a right circular cone As a uniform solid ($\frac{h}{4}$ from base, where is $h$ is height) and That composed of infinitesimally small ...
0
votes
1answer
41 views

Proving conservation of energy (kinetic + potential) in classical mechanics for an arbitrary system of particles?

For the case of a single particle in a potential $V$, it's simple : ${d\over dt} [{1 \over 2}mx(t)'^2 + V(x(t))] = mx(t)'x(t)'' - F(x(t))\ x(t)' = mx(t)'x(t)'' - mx(t)''x(t)' = 0$ But what about for ...
1
vote
3answers
85 views

Prove that the spacetime interval is not invariant under Galilean transformations [closed]

The spacetime interval $(\Delta s)^2 = (\Delta x)^2 + (\Delta y)^2 + (\Delta z)^2 - c^2(\Delta t)^2$ is invariant under the Lorentz transformation and this isn't the case for the Galilean ...
0
votes
3answers
627 views

Pendulum's motion is simple harmonic motion

For a pendulum's motion to be simple harmonic motion (S.H.M.) is it necessary for a pendulum to have small amplitude or S.H.M. can be produced at large amplitudes as well? If it is really necessary ...
-1
votes
1answer
46 views

I do not know whether i have solved this correctly. Can anyone help? [closed]

A cart is moving along the $x$-direction with a velocity of $4 \;\mathrm{m/s} $. A person on the cart throws a stone with a velocity of $6 \mathrm{m/s}$ relative to himself. In the frame of reference ...
1
vote
1answer
145 views

How are the watt-second, the newton-meter and the joule different?

The joule is $\mathrm{kg\,\ m^2/s^2}$ right? The watt-second is $\mathrm{J/s} \times \mathrm{s}$ thus $\mathrm{J}$. The newton-meter is $\mathrm{kg \,\ m/s^2} \times \mathrm{m}$ thus $\mathrm{kg \,\ ...
-1
votes
1answer
70 views

Motion on inclined plane

What has to be the conditions for an object of mass $m$ to move down an inclined plane with uniform velocity in terms of the forces acting in different directions on the object?
0
votes
1answer
72 views

What do we mean by the “load” on an engine?

In engines, we often talk about the load being something that acts against the rotating of the crankshaft. However, what does this mean in real life? In a car engine, for instance, what would the ...
0
votes
1answer
60 views

Driven harmonic oscillator problem : change of variables and expressing the extension of the spring

I'm struggling to understand the reasoning in question $b)$. Basically, I had to write Newton's Second Law and do a change of variables to put the equation of motion of a mass $m$ in a specific form, ...
0
votes
1answer
303 views

Spring-block system, simple harmonic motion, time period

In the case of simple harmonic motion of spring block system, why time period of the simple harmonic motion of the block is independent of acceleration of the system (spring-block system)?
0
votes
1answer
49 views

Newton's law of motion, pseudo force

Can we feel pseudo force just like the real forces?
1
vote
1answer
60 views

Distance between coils on a massive spring

I'm trying to calculate the separation between coils on a massive spring with no weights attached under different conditions. I will present my solution to the problem in the case of a uniform ...
0
votes
1answer
391 views

Finding torque due to normal force [closed]

A cubical block of mass $m$ and edge length $a$ slides down a rough inclined plane of inclination $\alpha$ radian with a uniform speed. Find the torque of the normal force acting on the block about ...
-2
votes
1answer
40 views

Time in a vertical circular motion [closed]

How can I calculate the time taken to go from one point to another, in vertical circular motion? If we have radius, angle between 2 points, and initial velocity. I tried to write $\frac{dv}{dt} = g \...
0
votes
1answer
31 views

Water Flowing In And Out Of A Basin

After a tap above a rectangular basin has been turned on, the basin fills in a time T1. After the tap is closed, opening a hole at the bottom of the basin causes the basin to empty in a time T2. If ...
2
votes
1answer
76 views

The role of mass in the tablecloth trick

Apologies if this has already been answered, but I have a question about the role of mass in the classic tablecloth trick, where the demonstrator pulls the tablecloth out from underneath a set of ...