# 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.

###### 1,295 Questions
Isaac Newton
Newtons Laws of Motion
Rotation

# How does newton's first law work?

Wt goes up must comes down

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Cars & Vehicles
Physics
The Difference Between
Rotation

# What is the difference between torque and horsepower in automobiles?

By Karl Brauer, Editor in Chief, Edmunds.com While horsepower is often considered when shopping for a vehicle, what about that "other" engine rating: torque? Specifically, what are the differences between horsepower and torque? If you flip through the pages of any automotive publication, you'll notice that these two measurements are commonly listed under vehicle specifications. And while the average car enthusiast knows that both horsepower and torque play a role in performance, most of them don't understand exactly how or why. Let's begin by explaining the technical difference between the two. Horsepower is defined as the amount of energy required to lift 550 pounds, one foot, in one second. From this definition you can see that the components of horsepower are force, distance and time. Distance and time are self-explanatory but force, specifically a twisting force, is what torque is all about. Remember that the initial energy that moves a car forward starts in the combustion chamber in the form of an explosion. This explosion forces a piston (or group of pistons) down in a straight line, which pushes on a connecting rod and turns the engine's crankshaft. It's this turning crankshaft where the twisting force of torque initiates. From there the force is carried through a flywheel, transmission, driveshaft, axle(s) and wheel(s) before moving the car. The measurement of torque is stated as pound-feet and represents how much twisting force is at work. If you can imagine a plumber's pipe wrench attached to a rusty drainpipe, torque is the force required to twist that pipe. If the wrench is two feet long, and the plumber pushes with 50 pounds of pressure, he is applying 100 pound-feet of torque (50 pounds x 2 feet) to turn the pipe (depending on the level of rust, this may or may not be enough torque). As you may have noticed, this measurement of torque does not include time. One-hundred pound-feet of torque is always 100 pound-feet torque, whether it is applied for five seconds or five years. So, if you want a quick answer to the difference between horsepower and torque, just keep in mind that horsepower involves the amount of work done in a given time, while torque is simply a measurement of force and is thus a component of horsepower. To see how torque and horsepower interact, imagine your favorite SUV (everyone has one of those, right?) at the base of a steep hill. The engine is idling and the gear lever is in the "Four-Low" position. As the driver begins to press on the throttle, the engine's rpm increases, force is transmitted from the crankshaft to each wheel, and the SUV begins to climb upward. The twisting force going to each wheel as the vehicle moves up the hill is torque. Let's say the engine is at 3,000 rpm, the gear ratio is 3, and the vehicle is creating 300 pound-feet of torque. Using the following formula, we can calculate horsepower: Take the torque of 300 multiplied by a shaftspeed of 1000 (3000 rpm divided by a gear ratio of 3) for a total of 300,000. Divide 300,000 by 5,252 and you get 57.1 horsepower that the SUV is making as it begins to ascend the hill. It is interesting to note that, since 5,252 is used to calculate horsepower by way of torque and shaftspeed, it is also the number in the rpm range at which torque and horsepower are always equal. If you were to view the horsepower and torque curves of various engines, you would notice that they always cross at 5,252 rpm. So now we have a technical understanding of how torque interacts with horsepower, but let's move beyond that to some real-world examples. For instance, we all know that a car moves from a dead stop in 1st or low gear, yet as the car's speed increases, the gears must be moved up through 2nd, 3rd and 4th to maintain acceleration. This is because at low speeds the transmission's gears work to transmit maximum torque from the engine to the wheels. You want this because it takes more force, or torque, to move a vehicle that is at rest than it does to move a vehicle in motion (Newton's 1st Law). At the same time, once a vehicle is underway, you want less torque and more horsepower to maintain a high speed. This is because horsepower is a measurement of work done and includes a time element (such as wheel revolutions per minute necessary to maintain 75 mph). Since entire books have been written on the concepts of horsepower and torque, it's not realistic to try and cover them fully in a single column. Finally, let me leave you with my favorite phrase about the relationship between horsepower and torque: Horsepower is what you read about, torque is what you feel.

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Rotation

# What kind of force that the tornado have like centripetal force centrifugal force?

Hi,

Well the force is centripetal force during a body is initially attacked by the tornado,when the body started swinging in the tornado from the surface of the earth,the time when body covers some distance from downward to upward is the time when centrifugal force is applied.... That means tornado have both the centripetal force and centrifugal force.....

Thanks you!

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Physics
Rotation

# Is there a maximum for angular velocity?

limited i think by the intrinsic ability of a rotating object to 'stay together'; i have the same problem when trying to determine the maximum rate at which a spinning rotor can rotate in a vacuum when there are no forces to stop it...for eg. in a suspended magnetic field. it's complex, but i think you must work out the lateral force due to the angular velocity and check it against the yield stress of the object.

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Physics
Chemistry
Example Sentences
Rotation

# What is a displacement can?

A displacement can is a can with a spout coming out one side at the top. When an object is placed in the can the water rises and runes through the spout at the top. collect this water in a beaker to see how much water was displaced.

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Physics
Mechanics
Rotation

# What is the relationship between feet pounds and NM for torque measurement?

1 foot-pound is equivalent to: * 1.3558179483314004 newton meter (exactly) found at www.wikipedia.org

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Fluid Dynamics
Kinematics
Rotation

# For a particle in circular motion the resultant acceleration is?

Since no values are given, the answer must be a general one. A particle in circular motion undergoes centripetalacceleration. Inertial motion is straight line motion. Any change in motion (including direction) requires positive or negative acceleration. In order to move along a circular (or any curved) path, a particle's direction of motion is in a constant state of diversion from straight line inertial motion, so it moves under a contant state of acceleration.

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Rotation

# Conservation of angular momentum tells us?

Angular momentum will not change unless an external torque acts upon the system

The short answer would be that angular momentum is conserved, i.e. it cannot be created nor destroyed.

A more technical answer would be that there is a certain theorem in theoretical physics called Noether's theorem which shows that if a physical theory exhibits rotational invariance (i.e. the physics are the same even if you rotate the system) that angular momentum conservation is a result.

According to particle physics therefore the conservation of angular momentum seems to tell us that the Universe is invariant under rotations. This might seem strange, because surely rotating yourself changes how think look, but the physics involved remains the same.

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Rotation

# Angular displacement symbol which represents it?

theta or θ

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Physics
Kinematics
Thermodynamics and Statistical Mechanics
Rotation

# How do you build a simple working model for physics?

COLING BELL give the lsit of working models in the wikipidea

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Physics
Rotation

# What is the torque value in in-lbs to turn a door knob?

Torque= length x force. Lenght is the distance to an object. Force must be perpendicularly acting on the object. In your question, you did not specify neither force and length of the knob. So I cannot give you a torque value. I believe the SI unit for torque is "Nm", assuming that you calculated your torque using all SI units. Then you have to convert Nm to pounds.

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Rotation

# Why is a whirlwind in a tornado fast?

The atmospheric pressure inside a tornado is very low compared to its surroundings, and that pressure drop takes place over a short distance. When there is a pressure difference between two areas it creates winds. The greater the change over a given distance, the grater the wind speed.

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Math and Arithmetic
Mechanical Engineering
Rotation

# How do you convert meters per second to RPM's?

You need more information to specify exactly what you are trying to do here, but I can give you one common example that will hopefully get you on the right track.

If you take the example of a cylinder spinning about it's axis, then you can convert between its rotational speed in revolutions per minute (RPM) and the tangential surface velocity (m/s) if you know the diameter of the cylinder. Essentially, you divide the time of one rotation into the circumference of the cylinder.

Legend:

V = tangential surface velocity

C = circumference of cylinder

D = diameter of cylinder

RPM = revolutions per minute

Pi = 3.14

Equations:

V = C * RPM = Pi * D * RPM

or

RPM = V / (Pi * D)

Example:

A cylinder with a diameter of 1 meter is rotating at 60 rpm. Its tangential surface velocity is:

V = (3.14) * (1 m) * (60 rpm) = 188.4 m/min = 3.14 m/s.

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Mechanics
Rotation

# What is the angular momentum of a photon?

The "intrinsic angular momentum" of particles is commonly called "spin". The spin of a photon is 1, in the units commonly used.

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Physics
History of Science
WW1 Allied Forces
Rotation

# What is centripetal force?

Centripetal Force is the force directed towards the center of an object's circular path. It makes a body follow a curved path.

Sir Isaac Newton stated: "A centripetal force is that by which bodies are drawn or impelled, or in any way tend, towards a point as to a center."

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Physics
The Difference Between
Rotation

# Difference between torque and moment?

Torque is a movement force. Moment is a static force.
Torque is often presented as Nm/revolution and moment is typically presented as Nm.
The words "torque" and "moment" (of force) mean the same.

However, "torque" tends to be used when there is an axle or pivot to be turned around, while "moment" tends to be used in essentially non-rotational situations, such as analysis of forces on a beam.

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Science
Physics
The Difference Between
Rotation

# What is velocity?

• Velocity is a physical vector direction quantity both magnitude and direction needed to define it.
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Equator
Rotation

# Which direction does the sink water spin on the equator?

The latitude has very little effect on the direction of sink water spinning. Please see the link below.

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Inventions
Math and Arithmetic
Physics
Rotation

# What is a velocity microphone?

A velocity microphone is a sensor whose electric output depends on the velocity of the air particles that form a sound wave . Examples are a hot-wire microphone and a ribbon microphone (bi-directional).
Velocity-sensitive microphones also respond much more to wind noise than pressure sensitive microphones (omnis). You get heavy bass tip-up or proximity effect if the sound source is close to the microphone. Cheers ebs

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Physics
Rotation

# What would happen if a disk one light second in circumference were to spin at 60 RPM?

60 revolutions per minute is one revolution per second.

1 light second is the distance light travels in one second.

What this means is that points on this hypothetical disk's perimeter would need to travel at the speed of light to satisfy your conditions. This cannot happen for anything that has mass.

Bottom line: a disk this size could not spin at this speed.

The answer to your question is that it would spin at the speed of light (It is hypothetical, so it doesn't matter that nothing can spin at that speed).

The shear forces would be so high before it could accelerate significantly that the disk would cease being solid and would break into trillions of tiny pieces. There is an awful lot of inertia in the outer rim of a disk that large! If it were created already spinning at that speed (by some miracle) it would take a practically infinitesimal time for centrifugal forces to make it explode violently into trillions of tiny pieces.

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Science
History of the United States
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Rotation

# What are some examples of centrifugal forces?

If you carry a bucket with say 1 inch of water, & you hold it the handle & down by your leg, you can do a centrifugal experiment. Hold tight to handle. Pretend your arm is the arm of an analog (older style) clock. Your goal is to spin the bucket of water in a Vertical circle w/o spilling any water. Tip: to develop enough speed you may have to swing the bucket forward & back a couple times. Keep in mind that generally your carrying arm will not be bent at the elbow (ie. keep arm fully extended, as much as

you can. I suggest you try this ONLY w/water & outside, for obvious reasons. Good luck!

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Physics
Rotation

# Is the net torque changed when a partner on a seesaw stands or hangs from her end instead of sitting?

The two factors that govern the torque or turning moment are her mass and the horizontal distance from the seesaw centre to her centre of gravity.

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Rotation

# What is centrifugal force?

Think of it this way. Let's say you have a yo-yo and let it unwind. Then you start swinging it around your head in a circle parallel to the ground. The force that keeps the yo-yo in its circular path is the centripetal force (centripetal = away from the center). Without it, the yo-yo would not continue in its circular path but would fly off in a straight line, which it is inclined to do. The tension in the string is the centripetalforce. The centrifugal force is a fictive force: it is, in fact, the "feeling of repulsion" caused by the yo-yo's inertia. Remember Newton's First Law : an object in motion tends to keep a linear path at a constant speed.

The fictitious (or apparent) force that appears to act away from the center of the point of application of the centripetal force is the centrifugal force; it's what you feel when you drive around a tight curve. Note that "nothing" is pushing you outward ... rather the car seat is pulling you inward.

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Mechanical Engineering
Rotation

# What is the difference between torque and bending moment?

torque-meant for curvilinear and moment for linear motions

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Calculus
Rotation

# What is meant by amplitude in simple harmonic motion?

Any simple harmonic motion is of the form x(t) = A cos(w t + a). Here the constant A with dimension [x] is called the amplitude.

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