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25 votes

Does the earth’s rotational angular velocity change?

The Earth is not a single rigid body, but consists of at least five separate regions which can move relative to one another. These are the crust (which is the region that we use to measure day length),...
  • 36.9k
12 votes

Does the earth’s rotational angular velocity change?

To add to @gandalf61's answer: You can also look up solar time. Due to the orbit around the Sun, the Earth has to rotate a bit more than 360° for the sun to get back to the same apparent position in ...
5 votes

Does the earth’s rotational angular velocity change?

There is no “gravitational” source of external torque acting on the earth Yes, there is. The tides are caused by the Moon's gravity. That energy has to come from somewhere. The drag caused by the ...
2 votes

Is torque possible without any pivot point?

You can calculate torque about any desired point; that point is not required to be pivoted. In $\vec{\tau} = \vec{r} \times \vec{F}$, vector $\vec{r}$ is the position vector of point where force $\vec{...
  • 230
2 votes
Accepted

Conservation of linear momentum in a rotating moon

"...but the moon does not have any linear momentum due to rotation" This is not correct. Why? At the moment a tractive force is applied through the wheels, and an equal and opposite force ...
  • 34.1k
2 votes
Accepted

Is torque possible without any pivot point?

I'm assuming that the only forces actually applied to the bar are P and Q as I show in FIG 1 below. Then you are saying equivalent result force is P + Q = 15 located at point C. But you didn’t go far ...
  • 58.5k
1 vote
Accepted

Relationship between net torque and net force in constrained systems

No, since you can have loading combinations that produce no motion. Specifically for the ladder problem, consider the kinematics. Points A and B are only allowed to slide, which means the center of ...
  • 34.1k
1 vote

How the calculate and/of measure the applied force between a motor and a flywheel?

Make a basic free body diagram. From the top down you have the following geometry and forces. I have separated the two bodies for clarity. Point A is for actuator, point B for bearing and point C for ...
  • 2,787
1 vote

Is torque possible without any pivot point?

The acceleration of the center of mass (CM) is determined by the net external force. The net torque is the change in the angular momentum if you use the CM as the point about which to evaluate torque ...
  • 7,036
1 vote

How to draw vectors?

For one thing, if $F_x$ and $F_y$ are components of $\vec F$, they are usually drawn not to extend beyond the projection of $\vec F$ in that direction. E.g. the $F_x$ arrow in Fig 1 should be much ...
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