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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

Types of centrifugal force?

Centrifugal force can refer to two types: 1) Pseudo centrifugal force, which is the perceived force felt in a rotating reference frame due to inertia, and 2) Centrifugal force in mechanics, which is the outward force experienced by an object moving in a curved path.

Can two forces of equal magnitude and direction exert different torques on a object?

Yes, two forces of equal magnitude and direction can exert different torques on an object if they act at different distances from the axis of rotation. The torque produced by a force is proportional to the magnitude of the force and the perpendicular distance from the force to the axis of rotation.

A ball rolling across the floor slows to a stop because?

it experiences friction between the ball and the floor, which causes a force opposing its motion. This force gradually dissipates the ball's kinetic energy, eventually bringing it to a stop.

A bicycle wheel rotates uniformly through 2 revolutions in 4 seconds What is the average angular speed of the wheel?

The average angular speed is the total angular displacement divided by the total time. Since the wheel completes 2 revolutions (2 x 2π) in 4 seconds, the total angular displacement is 4π. Thus, the average angular speed is 4π/4 = π radians per second.

F equals ma in linear and Rotational force equals I x alpha. And torque for linear T equals max R. why rotational torque is I x alpha?

I'm going to let Paul A. Tipler (Aka my 50lb physics textbook) answer this one.

First to explain why I (rotational inertia) is in the equation.

T (not period, but tao, or torque) is defined as F x R

By Newton's second law F = ma, in a rotating body a = alpha x R

F = m(alpha)R

if you multiply both sides by R

F x R = m(alpha)R2

Recall F x R is T

T = m(alpha)R2

Sum the torques in the entire body

Sigma(T) = Sigma(mR2(alpha))

Therefore I is defined as Sigma(mR2), or for a continuous object(a disk) I = the Integral of (R2dm)

Therefore, Sigma(T) = I x alpha

This is analogous with Newton's second law: F = ma. Where in rotation F --> T, m --> I, a --> alpha

What is the difference between torque and horsepower?

Horsepower - power over time, continuously used. You can only generate what you need or use.

Torque- Power on hand, waiting for demand. Like a weight hanging on stick. It is there when you need it.

Torque gets you going and Horsepower keeps you rolling.

Answer

You really should be asking, "What is the difference between torque and power?"

Horsepower is simply the Imperial unit of measurement for power, usually used to describe the output (rather than input) power of a machine. These days, most countries use watts, which is the SI unit for power. Power is defined as the rate of doing work. In Europe and elsewhere outside North America, the output power of a car engine is measured in kilowatts, rather than in horsepower.

Torque is the product of the radius of rotation and the force acting at right angles to that radius. So, torque is normally expressed in newton metres.

The work done by torque can be determined by multiplying the force acting at right angles to the radius, by the circumference through which that force acts. If we know the time taken to complete the circumference, then it is possible to determine the power.

Does linear motion have angular momentum?

I believe that any particle in linear motion must also have some angular momentum because all particles have spin. In the case of a photon the spin, wavelength and angular momentum all vary with the relative linear velocity. So in my point of view time itself is the ratio between relative linear and angular momentum.

A bolt needs to be tightened with a torque of 35 N-m You use a 25 cm wrench and pull at an angle of 60 degrees how much force do you need to exert?

To calculate the force needed to tighten the bolt, use the formula:

Force = Torque / (Wrench length * sin(angle)) Force = 35 N-m / (0.25 m * sin(60 degrees)) Force = 141.42 N

Therefore, you would need to exert a force of approximately 141.42 N to tighten the bolt.

Can you spin faster with your arms open?

If you've ever watched an Olympic ice skater do a spin, you may have noticed that he or she will draw in her arms closer to her body in order to increase the speed of rotation. This is in keeping with the law of the conservation of angular momentum.

Does angular momentum requires an inertial frame?

Yes, angular momentum is conserved in an inertial frame of reference, where Newton's laws of motion hold true. In a non-inertial frame, the concept of angular momentum becomes more complex due to the presence of fictitious forces.

Which scientists discovered that toys use the principle of centrifugal force?

There isn't a specific scientist credited with discovering that toys use the principle of centrifugal force, as this concept has been known and applied in various fields for a long time. Toys such as spinning tops, yo-yos, and fidget spinners utilize centrifugal force to stay balanced and spin for longer periods of time.

What is the meaning of centripetal force?

Answer It is the force which keeps a body moving in circular motion. Centripetal force is the force that acts opposite to cetrifugal force. Centripetal force is a real force. Centrifugal force is a pseudo-force

How is centripetal force a newton?

Centripetal force is a Newtonian concept because it follows Newton's laws of motion. It is the force that keeps an object moving in a circular path and is directed towards the center of the circle. According to Newton's second law, acceleration is directly proportional to force, so centripetal force is needed to accelerate an object towards the center of the circle.

How is mechanical tachometer used for measuring angular velocity?

A mechanical tachometer typically uses a rotating shaft connected to the moving object to measure its angular velocity. As the object rotates, the shaft spins and moves the pointer on the tachometer dial, displaying the angular velocity in revolutions per minute (RPM). The speed of rotation is directly proportional to the angular velocity of the object being measured.

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

What is the meaning of 'galvanizing force'?

A galvanizing force refers to something or someone that energizes or motivates others to take action or change. It is a catalyst that inspires people to come together and work towards a common goal.

What are torque specifications for one-inch stainless steel bolt versus a steel bolt?

Torque is difficult value to estimate. Especially, for material like stainless steel. There are many factors that effect the value of torque. One of the biggest variable is friction. Since this is almost impossible to control in "field" applications, it is crucial take this into consideration when designing bolt connections.

What is shaft power and how is it different from torque of a motor?

Fundamentally: power = torque x rpm Power and torque both make noise, but they are different in how they are measured and what they mean. Torque is not related to time. Power is a time-related rate. Most engineers talk about torque when they need to understand how much force is applied from a dead stop. It is force X radial distance. Huge torque may have very little power (in HP or Watts) behind it. Imagine a really strong guy with a really long wrench unfastening a bolt. He can develop lots of torque, but ultimately he can put out very little power (about 1/4 HP or 185 W for humans) over an extended time.

How much torque is exerted by human muscles?

The amount of torque exerted by human muscles can vary greatly depending on the individual, the specific muscle group being used, and the type of movement being performed. On average, the peak torque generated by major muscle groups during activities like lifting weights or pushing/pulling objects can range from about 100-200 Newton-meters (N-m). However, this can be significantly higher for elite athletes or in certain specialized circumstances.

Why centripetal accleration is measured in grams?

Centripetal acceleration is measured in meters per second squared (m/s^2), not in grams. Grams are a unit of mass, not acceleration. The centripetal acceleration of an object is the rate at which its velocity is changing direction as it moves in a circular path.

What are Centripetal and Centrifugal forces work?

Center of gravity toward the center of the body absorbs. Centrifugal force away from the center of the object.

Centripetal force is real. Centrifugal force is made up and doesn't exist.

Is screw force the same as screw torque?

No, screw force and screw torque are not the same. Screw force refers to the axial force applied along the axis of the screw, while screw torque refers to the rotational force needed to tighten or loosen the screw. Torque is calculated by multiplying the force applied and the distance from the axis of rotation.

Can both centripetal and centrifugal force act at a body at same time?

No, centripetal force is required to keep an object moving in a circular path by pulling it towards the center. Centrifugal force is a virtual force that appears to push an object away from the center due to its inertia. Both forces cannot act on the same object simultaneously as they are related to each other through Newton's third law.

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.

What is velocity?

Velocity is a vector quantity that describes the rate of change of an object's position. It is defined as the displacement of an object per unit of time in a specific direction. In simpler terms, velocity tells us how fast and in what direction an object is moving.

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