Questions tagged [newtonian-mechanics]
Newtonian mechanics discusses the movement of classical bodies under the influence of forces by applying Newton’s three laws. For more general concepts, use [classical-mechanics]. For Newton’s description of gravity, use [newtonian-gravity].
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Difference between change in momentum caused by a force and by kinetic energy
I don't see what the difference is between a momentum change caused by a force (eg: someone pushing against a metal ball) and and by transmission of kinetic energy (eg: a metal ball hitting another ...
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Centripetal force pointing outward
What's going on physicists.
I would like some explanation here. I haven't been satisfied with the ones I gathered on the internet.
Here is it:
If a particle moves in circular motion, there will be a ...
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Conceptual doubt related to motion of two blocks on an incline
I was solving the following question:
In the arrangement shown in the figure all surfaces are smooth. Select the correct alternative(s)
(A) for any value of θ acceleration of A and B are equal
(B) ...
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Is gravitational potential energy of body by $mgh$ negative? [closed]
Potential energy is found by two formulas:
$P.E=mgh$ (in earth, at acceleration g)
$P.E=-Gm1m2/r^2 * h \approx -Gm1m2/r$
I am not worried about the approximation of h=r, or use of g in earth, My ...
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Does A Pivot Exert A Force
On a frictionless horizontal table, a uniform stick is pivoted at its middle, and a ball collides elastically with one end, as shown in Fig. 8.10. During the collision, what are all the quantities ...
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Why particle is certain to escape the conservative field when the mechanical energy is positive?
It is generally said that the particle is bound into the conservative field when the mechanical energy is negative and zero is the limiting case and the particle will escape the field when the ...
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Interesting Aerofoil Logical Fallacy
I am new to physics in general having just finished AP Mechanics and have limited knowledge of how fluid dynamics work. But just using forces and a simplified understanding of drag if have come to the ...
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Person holding two persons hanging over the edge and centre of mass inconsistency
Imagine a person holding the leg of the person in front that also holds the person in front of him. (over the edge like in MI4, assume centre of mass of second person with feet still on the floor is ...
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Buoyancy basics
I was solving this question and in the solution, they have applied a buoyant force exerted by kerosene. It makes sense by the basic definition of the buoyant force from Archimedes principle. However, ...
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Direction of friction of a block moving down a plane
Lets say that there is a block is on an incline, but given a horizontal push before being let go. Once the block is let go, friction will oppose the component of gravity acting along the ramp, $mg\sin(...
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Why doesn't Car-Parrinello molecular dynamics require an SCF calculation?
Reading the various terms of the Lagrangian in Car–Parrinello molecular dynamics, I'm trying to understand why there is not an SCF procedure hidden there.
In fact, it seems to me like the second term ...
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Would a homogeneous rod on a fulcrum oscillate or remain at rest after displacement?
If I take a homogeneous rod, put it on a fulcrum, push one side down in a controlled way and release very carefully won't the rod just stay at rest in that new position? ChatGPT says that it would ...
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A bird in a container [duplicate]
Suppose there is a bird in a sealed container, and the container is on a scale that measures its weight. The bird is flapping its wings to hover in the middle of the container. If the bird flaps its ...
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Vertical Circular Motion ($u$ minimum)
In vertical circular motion, when we consider motion of a pendulum bob, while finding minimum velocity to complete VCM, we take Tension=0 at highest point and velocity at highest point is not equal to ...
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Granular Material Piles on an Inclined Plane
Consider a conical pile of sand (or any other granular material) that is placed on a flat surface. This conical pile has a given radius and height (r and h, respectively). What would the effect be on ...
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Conservation of linear vs. angular momentum in two similar cases
I have a question that eludes my understanding:
Imagine we have a bullet of mass $m$ and a rigid pendulum with a bob of mass $M$ hanging from a rigid rod of negligible mass hanging from the ceiling ...
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A Force Perpendicular to the Velocity changes only the direction of motion? [duplicate]
Why does a force that remains perpendicular to velocity alaways only change the direction of the motion(circular) and not induce a velocity in the perpendicular direction???
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How to understand gyroscopes by using vectors?
I’ve seen plenty of videos explaining how gyroscopes work, but almost non of them why they are constrained to work in such way. From seeing only angular momentum vectors, how could one predict ...
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What would happen to the moon's orbit if we reduce (instantaneously) its mass? [closed]
In my opinion the moon's orbit shouldn't change, because an orbiting body is a free falling object and the trajectory of a free falling object is not affected by its mass (because the inertial mass ...
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Is the kinetic energy of a rotating system just the sum of the instantaneous kinetic energies of the individual particles?
Take a look at this construction which shows linearly moving particles giving the illusion of circular motion. (Follow the instructions on the screen).
Now the question is when I calculate the total ...
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Mapping between generalized forces and external torque of a rigid body whose rotation is described by quaternion is not unique(?)
In this paper the mapping between generalized forces and external torques for a rigid body (when the rotation is described by a quaternion) is derived:
$$\textit{F}_Q = 2\textbf{G}^TT'$$
where $\...
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Why can we treat a ball as a point mass to calculate torque?
A sphere of radius $R$ is supported by a rope attached to a wall as shown in the below figure. The rope makes an angle $\theta$ with respect to the wall. The point where the rope is attached to the ...
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Relative acceleration, mechanics
Consider a system of two objects with mass $M, m$ as presented below.
Assume that there's no friction between both the surface, M and between M, m. I'm asked to find the acceleration of m, M using ...
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Spring potential energy, conversion
I have a physics problem in my book, where a spring is compressed and a ball is laying in the end of the spring. When the spring is released the ball will reach a certain speed. In the solution it ...
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A paradox while explaining the equilibrium of books
An even number of books (say four) are held in the manner shown in the figure. It is obvious that if we apply a large force inwards, we can increase the normal force, and hence the friction which ...
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Confusion about sign conventions used in the Doppler formula
Wikipedia gives the Doppler formula as:
$ f = \left( \frac{c \pm v_r}{c \pm v_s} \right) f_0 $
c is the propagation speed of waves in the medium.
$v_r$ is the
speed of the receiver relative to the ...
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Work Done by kinetic friction in Circular Motion
We know when an object is moving in a circular motion on a rough horizontal surface, direction of kinetic friction is constantly. Thus, fto calculate the work doen by friction, we need to use ...
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Tension of rope over frictionless edge obstructing block
Consider the diagram below. All corners are assumed to have no friction. Is it true that the tension throughout the rope is equal in all sections? The section over the edge of the building, the ...
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Does a rocket moving in a circle expel exhaust at a greater velocity?
Consider a rocket undergoing constant acceleration in a rectilinear path. Assuming the rocket is ideal (ignoring fuel mass and energy loss such as sound, radiation, vibration, etc.) a portion of the ...
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What is a simple example that contradicts the theory that light (photons) could have a super small mass? [duplicate]
The obvious example is that, to bring something that has mass to the speed $c$ requires infinite energy due to special relativity. But what if a kid asked me "What if light/photos had a super ...
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Strain energy stored in a bungee cord pulled at its midpoint [closed]
A bungee cord that behaves elastically has an unstressed length $L=.76$ m and a stiffness $k=140$ N/m. The cord is attached to two pegs, distance $b=.38$ m apart, and pulled at its midpoint by a force ...
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Doppler shift from a moving reflector and source if only the relative velocity is known?
Suppose there is a device which is producing and listening to sound (sonar), a reflector is moving with respect to device and the velocity of reflector and device with respect to the air is not known, ...
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What does it mean when vector quantity is negative?
I’ve seen in some problems that vector quantity is negative. For example, negative Coulomb means that two charges attract… negative acceleration means that object is slowing down. However, magnitude ...
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Buoyant force on a stick making an angle theta with the vessel
I was solving this question
The answer of the question uses balancing of torques.
It uses $L=0.5$m
I have problem with the fact that they have used buoyant force $F = \rho V g$. Marking the net ...
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Doubt on conservation of angular momentum for Kepler's laws
Just before proving Kepler's laws, my Professor claimed that if $\vec{F}$ is a central force with center $O$ and it is the only force acting on a point $P$, then the trajectory of $P$ is a curve plane....
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Idealized Newton's cradle
I was wondering about the conditions for an ideal newtons cradle.
Under regular circumstances, the collisions are inelastic and a newton's cradle dissipates energy in various forms like heat, friction,...
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Why is it less shocking to cross the bump with just one wheel? [closed]
Difference between 'go over speed bump with one side' and 'both sides at the same time'
I asked a similar question previously and received an excellent answer stating that when going ...
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Condition for a car moving with a constant velocity [closed]
I seek your help with this simple yet confusing problem. The question says:
A car is moving with a constant velocity 10m/s. Which one is correct?
No force is acting on the car
The force applied by ...
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When an object is thrown towards the sky it starts to gain potential energy, why?
I didn't think so because when an object is thrown towards the sky it already has kinetic energy and it looses it's energy due to the gravitational force of the earth.
When the object looses all of it'...
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Tendon excursion method application/alternative for joint represented by quaternion in biomechanics
I am building a biomechanical model that consists of spherical joints. I wanted to represent these spherical joints by quaternions. I am struggling to derive how the muscles contribute to the ...
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Can photons interact with one another? [duplicate]
Photons can interact with matter, particles, nuclei, etc.
But can they interact with one another?
By interaction I mean any kind of physical interaction: Momentum/Energy transfer, electromagnetic ...
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Throwing a ball in the air
When we throw a ball in the air, we know that if we do not throw it too high, then g can be held constant over the trajectory and we can approximate the curve by a parabola. However we also know that ...
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Is it necessary that a force must cause a change in either velocity, shape, or size?
Our physics teacher made us define a force as
“A push or pull, which causes at least one of the following- Change in velocity, change in shape, change in size”.
If I push a wall really hard such ...
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Can the motion of a rigid body be decomposed into translational and rotational motion about ANY point?
My textbook mentions Chasles' theorem which asserts that
" it is always possible to represent an arbitrary displacement of a
rigid body by a translation of its center of mass plus a rotation
...
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What does $v$ actually represent in pulley problems?
Let us consider the problem of two pulleys with boxes attached to their ends. One pulley is movable, and the other is not. The problem requires us to find a relationship between velocities of these ...
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3-stage rocket payload problem [closed]
A rocket goes to the sky, and undergoes 3 stages. I want to find the payload of it.
In stage 1, 80% of the mass is the fuel, 10% of the mass is dry mass, and 10% is the remaining rocket. Similarly, in ...
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Local vs distant gravity effects where is the boundary line of effective control? [closed]
I'm not one of the 'gravity is only a theory' crowd or a flat earther that thinks gravity is fake and that down is always down. but thinking about gravity and what has been put forward by many great ...
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Why do objects in circular motion move outwards instead of inwards? [duplicate]
I know that whenever an object undergoes circular motion then it has a centripetal acceleration towards the centre and a tangential acceleration. Due to these accelerations I had thought that ab ...
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Spinning a rope conundrum
Sometimes I will take a rope or string and spin it in the air to see what will happen. Now usually, if I am spinning it vertically, the end of the rope will extend outwards due to Newton's first law, ...
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Issue with simplifying the equation related to non-uniform acceleration
I am exploring how the cross sectional area of a drogue chute affects its velocity after travelling a set distance.
I got this equation:
$$m_1 a = m_2 g - \frac12 c_d \rho A v^2,$$
This covers the ...
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