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Rotation

Classical mechanics doesn't just describe how an object's position behaves under external influences, but also how its orientation behaves. Using the same principles found in Newtonian mechanics, laws and relations governing rotation can also be derived. Please direct all your questions about moments of inertia, angular velocity, angular momentum, centripetal force, centrifugal force, torque, and spin here.

645 Questions

Why did my physics teacher make me write centrifugal force is a figment of my imagination and centripetal force is real?

Because there is no centrifugal force. The force of circular motion is inward, thus centripetal. If you are on a car that makes a quick right turn, you feel a "centrifugal" force leftward. But in reality, it is the car making an acceleration to the center of the curve, which is to your right. What you feel is inertia, not a force.

What is clockwise and anticlockwise torque?

Clockwise, top rotating to the right, and counterclockwise, top rotating to the left is only a perspective based on the position of the observer. The torque is the rotational force of the rotating object. Most often the perspective of the observer is from the driving end of a shaft facing the driven machine. The amount of torque at a given speed of the driving machine (engine or motor) is mechanically converted into work by the driven machine (generator, pump, compressor...etc.).

Why it is not easy to whirl a hammer by a longer chain?

Whirling a hammer with a longer chain requires more force due to the increased inertia of the longer chain, making it harder to achieve the necessary speed and control to keep the hammer moving in a circular motion. The weight of the hammer at the end of a longer chain also creates a larger centripetal force that needs to be countered by the person whirling it, adding to the difficulty.

What is external bending moment?

External bending moment is a force applied to a structural member that causes it to bend. It results in a combination of tensile and compressive stresses on the material of the member. External bending moments are important considerations in the design of beams and other structural elements to ensure their ability to resist bending and carry loads.

Are revolution and rotation the same?

No, revolution and rotation are not the same. Revolution refers to an object's motion around an external point or axis, while rotation refers to an object spinning around its own axis. Rotation typically occurs within the object itself, while revolution involves movement around an external point or center.

Why is angular momentum of a body is equal to the product of its moment of inertia and angular velocity?

Angular momentum about the axis of rotation is the moment of linear momentum about the axis. Linear momentum is mv ie product of mass and linear velocity. To get the moment of momentum we multiply mv by r, r the radius vector ie the distance right from the point to the momentum vector. So angular momentum = mv x r

But we know v = rw, so angular momentum L = mr2 x w (w-angular velocity)

mr2 is nothing but the moment of inertia of the moving body about the axis of rotation.

Hence L = I w.

Is centrifugal acceleration a uniform acceleration?

No, centrifugal acceleration is not a uniform acceleration. It is a type of acceleration that occurs when an object moves in a curved path and experiences an outward force away from the center of rotation. The magnitude of centrifugal acceleration changes as the object's speed or radius of rotation changes.

When a particle move in a circle then angle between linear velocity and angular velocity?

The angle between the linear velocity and angular velocity of a particle moving in a circle is typically 90 degrees. This means that they are perpendicular to each other.

What is dimension of angular velocity?

[ T-1 ] . Reciprocal time, from "degrees per second" .

The angle part of it is dimensionless.

If you know the coefficient of friction how do you find the maximum velocity to maintain a circular path at a given radius?

say mass(m) = 10 kg, radius(r) = 10 m, say friction coefficient = 0.5

force to break friction = 10 * 0.5 = 5 kgf = say 50 n

to find acceleration required to produce this force use f=m*a, shuffle to a = f / m

so a = 50 / 10 = 5 (m/s)/s, install in a = v^2 / r, so 5 = v^2 / 10,

so 10 * 5 = v^2, so sq. root 50 = v, so v = 7.07 metres / second

if friction coefficient and radius remain the same, altering the mass wont alter the velocity at breakaway point

What is angular velocity in physics?

It means how fast something rotates. Rather than taking the linear speed (meters per second, or some other common unit of speed), the angular velocity is specified in radians per second, degrees per second, revolutions (full turns) per minute, or something similar. By this definition, each part of a solid, rotating object rotates at the same angular speed.

What is the angular momentum of a 0.730 kg ball rotating on the end of a thin string in a circle of radius 0.950 m at an angular speed of 14.7 rad per second?

the angular momentum is given by:

.

L = mass (m) * velocity (v) * radius (r)

you have the mass and radius, so to calculate the velocity:

.

circumference = 2 * pi * r = 2 * 3.1416 * 0.95 = 5.969 metres

14.7 rad / sec = 2.3396 rev / sec

so velocity = circumference * rev / sec = 2.3396 * 5.969 = 13.965 metres / sec.

so:

.

L = m * v * r = 0.73 * 13.965 * 0.95 = 9.685 n-m-s

Why does the bob of a swinging pendulum comes to rest after sometime?

The pendulum bob comes to rest due to air resistance and friction in the pivot point, which gradually slows down its motion. Additionally, energy is transferred from kinetic energy to other forms of energy like heat, causing the pendulum to eventually stop swinging.

What are the things you need for a time machine?

The first thing you'll need is a lot of patience, as you wait for somebody to invent it.

I have to tell you, though, that there are currently no serious efforts in that direction,

by anyone reasonably comfortable with the laws of Nature and in possession of all of

his wits and faculties.

What is the direction of angular velocity?

The direction of angular velocity is perpendicular to the plane in which the rotation is occurring. It follows the right-hand rule, with the thumb pointing in the direction of the axis of rotation and the fingers curling in the direction of the angular velocity.

Does a bar magnet exert a torque on itself due to its own magnetic field?

Yes, a bar magnet can exert a torque on itself due to its own magnetic field. This torque can cause the magnet to align itself in a specific orientation, depending on the interaction between its north and south poles. If the magnet is not free to rotate, this torque can manifest itself as a force causing the magnet to move.

Why a body in uniform circular motion experiences a force?

A body can execute circular motion only if there's a force acting on it, directed

towards the center of the circle. Without that force, circular motion isn't possible.

If you expected us to get into "centrifugal" force, forget about it. No such force exists.

Is gear a force multiplier or a speed multiplier?

Both. A small driving gear and a large driven gear is a force multiplier. Whilst a large driving gear and a small driven gear is a speed multiplier

What is dimension of angular momentum?

The dimension of angular momentum is kg m^2/s.

What is gyromagnetic resonance in the ferrites?

Gyromagnetic resonance in ferrites is a phenomenon where the magnetic moments of the atoms in the material precess around an applied magnetic field at a specific frequency. This resonance occurs due to the interaction between the material's electron spins and the external field and is commonly used in applications such as microwave devices and magnetic storage media.

When is the angular momentum of a system not conserved?

The angular momentum of a system is not conserved when external torques are applied to the system. These torques can change the angular momentum by causing the system to rotate faster or slower or by changing the direction of its rotation.

Is Centripetal force causes an object to accelerate in a fixed direction true about centripetal force?

Yes, the statement is true. Centripetal force is a force that acts towards the center of a circular path and is responsible for changing an object's direction, rather than its speed. It keeps an object moving in a circular path by constantly pulling it towards the center of the circle.

Where is the angular joint in a human?

The angular joint in a human body is located at the elbow, where the forearm can bend and straighten.

What is the difference between torque and moment of inertia?

Torque is the measure of the rotational force applied to an object, causing it to rotate around a pivot point. Moment of inertia, on the other hand, is a measure of an object's resistance to changes in its rotational motion. Torque depends on force and the distance from the pivot point, while moment of inertia depends on an object's mass distribution and shape.

What is breakaway torque?

Breakaway torque is the amount of torque required to overcome the static friction of a stationary object and set it in motion. It is a measure of the minimum force or torque needed to break something free from its initial position.