# Tag Info

69

No, a car cannot steer on a frictionless surface. This has little to do with gyroscopic action and more to do with conservation of momentum: to turn, even when conserving its speed, the car needs to accelerate at right angles to its motion, which changes the total momentum of the motion. This change in momentum requires a force which, in normal roads, is ...

50

If the wheels had spun fast enough for a gyroscopic effect to become noticeable, the only result on a frictionless surface (which would be the same without a surface at all) is that when you turn the wheels, the rest of the car would rotate instead of just the front wheels :) You need some reaction force to alter the trajectory, like a sail or surface ...

28

Yes you can It is actually possible with a real car, but you would have to be very patient to steer a little bit. Suppose you have built a car with power on the big front wheels to induce a gyroscopic effect. If you rotate the wheels, the direction in which the center of mass is going will not change directly, but the angle in which the rest of the body ...

20

Short answer: it cancels the gyroscopic effect (with caveats). As long as the system holds together (see below), if the two halves spin with exactly the same magnitude but opposite sign angular momentum, from the point of view of an outside observer, the system behaves like one of zero angular momentum. In particular, it takes negligible torque on the part ...

19

Actually reaction wheels or control moment gyros are only part of the answer. To maintain the the accuracy and precision on the order of what Hubble demands requires a fully integrated Feedback Control System of actuators and sensors. For microradian pointing, reaction wheels provide only the first stage of isolating disturbances in a multi-stage pointing ...

11

They use reaction wheels, which are a type of flywheel to stabilize many spacecraft. For missions that need to be extremely stable (i.e., any mission with telescopes like Hubble), they try to avoid using the thrusters as these cause small vibrations to "ring" throughout the spacecraft. The vibrations can last for relatively long periods of time on some ...

10

Since there is no friction, then it will not affect any other forces that may act on the car. The direction of wind blowing on the car may change its trajectory, as any driver will attest when driving in high winds. Turning the car wheels may have a slight affect on the resultant direction of the force. If the car has curved roof, then it may acts as wing. ...

9

The torque that rotates a top upright, as happens in that youtube video, is due to sliding friction between the top and its supporting surface. Crucial to this effect is the fact that the top in that youtube video has a rounded bottom, instead of coming to a sharp point at the bottom like some tops do. The effect is more pronounced and dramatic in tops ...

8

Reaction wheels, momentum wheels, and control moment gyros are three somewhat distinct ways of controlling the rotation and orientation of a spacecraft. Reaction wheels are the easiest to understand, at least in their simplest form. Consider a spacecraft such as a space telescope that is nominally not rotating with respect to inertial space. The reaction ...

8

It's really hard to build an ideal gyroscope. Forces such as friction will tend to cause problems that make the unit precess. Such errors need to be corrected over time if you want to use it as a navigation instrument. For airplanes, that means that the gyroscopes that drive the artificial horizon are not unconstrained. A simple gyroscope with full range ...

7

A gyroscope maintains its orientation with respect to any inertial reference frame. An inertial reference frame is one in which objects with no force on them remain at rest or in uniform motion (i.e., moving in a straight line with constant velocity).

6

The reason why a gyroscope does behave in this strange way is that if you try to rotate it's axis in some direction, the "endpoints" of this axis have to be pushed perpendicular to what our first intuition would say. In order to verify why the axis starts rotating in this strange way, let's make some simplifications: the gyroscope consists of two identical ...

5

You seem to be saying that friction couldn't speed it up, because nothing else is moving that fast. Well, how fast is it moving? We can imagine the gyroscope axis parallel to the z axis, and the casing to be aligned such that the x axis goes through it. If the casing is tipped slightly, the gyroscope resists that turning and one side of the shaft has firm ...

5

You are partially correct. If you have two objects with moment of inertia $I_1$ and $I_2$ then if one applies a torque to the other, they will start rotating in opposite directions. So if one object is the reaction wheel and the other is the satellite, the satellite will indeed rotate (while the reaction wheel, internally, is rotating in the opposite ...

5

The Earth's tilt doesn't change so much as it's position around the sun changes. Notice the North Pole sees more sun in summer than in winter cause it's tilted towards the sun in summer but not in winter. The north pole always points in the same direction into space pretty much. It wobbles slightly, and quite slowly, completing a full wobble every 41,...

5

The centre of mass of the rod and the spinning disc drops a little. Thus there is a loss of gravitational potential energy and a gain in the precessional kinetic energy. You can think of it as the torque which is causing the precession rotating through an angle and so work is done by the torque which increases the rate of procession. The change of angle ...

4

In general, a spinning top will exhibit three types of motion. First, it will rotate about its axis. Secondly, if a constant force is applied, this axis may precess around the direction a of the force. Finally, there is a process called nutation in which the angle between the axis of rotation and the force oscillates, creating a 'wobbling' motion. When the ...

4

This gyroscope precession isn't very intuitive but you can understand in terms of rotational motion that you probably do have an intuition for. As the torque from the supporting cable tips the wheel, the lower part of the wheel becomes closer to the vertical axis and the upper part becomes further away. As you bring something closer to the axis it speeds up ...

4

yes it would. Although they tend to drift a bit over time anyway in practice.

4

Torque requires a force that is applied to a lever arm. The quoted statement is saying that the gyroscope is free to rotate about the axis AB, meaning that no rotational force can be applied to it as long as it is free to rotate. With no applied force, there can be no applied torque.

3

Veritasium has made a video about this. With this as a solution video. Someone also posted this video response, which also has a good explaination. Even though they use a disk with a unbalanced center of mass, the same still applies to your ball. The rotating ball will try to rotate around its center of mass. However if this does not align with the point ...

3

Friction is the only force that would cause the car to move along a different path. On a frictionless surface, the gyroscopic effect could change the orientation of the car a bit, but not the trajectory of the car. In other words, the front car would no longer point along the direction of travel, but would "skid". (That is, if you could call frictionless ...

3

On a completely frictionless floor, with the absence of other external forces, the centre of mass of the car will continue in the same trajectory for ever. Hence no steering is possible. However, irrespective of whether the front wheels are rotating or not, turning of the front wheels will produce a counter torque changing the orientation of the car, albeit ...

3

OK... once more: let's assume we are looking at a map-coordinate system where the x-axis points East, the y-Axis points North and the z-axis points towards the zenith. In such a system there are three acceleration components $\{a_E, a_N, a_Z - g\}$. Since the surface of the Earth is not an inertial system, the gravity of Earth always acts on the Zenith ...

3

By way of analogy, does your car spin? Your car might well go into a spin if you try to turn while driving over a patch of black ice, but that isn't a desirable outcome. Humans have developed lots of schemes to avoid undesired rotation. This is particularly so with satellites. You will find lots and lots of articles about controlling the attitude and ...

3

Yes comets spin. Satellites do too - typically they are set to spin in such a way as to point to earth at all times - which means they spin once per orbital revolution. Often small adjustments are made with the use of reaction wheels - move the wheel one way and the satellite turns the opposite way. There is no reason why any object should have to have any ...

3

The top is a symmetric rigid body. The equations of motion of a rigid body around its center of mass are given by: (Please, see for example: Marsden and Ratiu , (page 6). $$I_1\dot\Omega_1=(I_2-I_3)\Omega_2\Omega_3$$ $$I_2\dot\Omega_2=(I_3-I_1)\Omega_3\Omega_1$$ $$I_3\dot\Omega_3=(I_1-I_2)\Omega_1\Omega_2$$ Suppose that the rigid top is symmetric about ...

3

A gyroscope tends to stay fixed relative to it's original direction of spin (angular momentum vector direction). If a torque is applied it will show some resistance. In some scenarios that torque can be applied by the force of gravity. There are countless scenarios in which other forces can be involved.

Only top voted, non community-wiki answers of a minimum length are eligible