I am trying to understand the relationship between `v`

and `q̇`

using the functions that provide the Jacobians relating the two and I wonder if someone could explain the meaning of the required velocity ranges?

The docs say:

```
Return the range of indices into the joint velocity vector ``v`` corresponding to joint `joint`.
```

E.g. For the second joint in my robot I get:

```
julia> state.vranges[jointVector[2]]
2:2
julia> velocity_range(state, jointVector[2])
2:2
```

The range is a set of indices but I don’t understand how a one-dimensional joint can span more than one index at a time. The result is always a one-dimensional Jacobian `J = 1.0`

which seems to imply that `v == q̇`

for all my joints (none are planar). Use case: I am using RBD in a state-estimator and I need to compute a number of variables to compare with the corresponding measurements from sensors.

BTW: noticed in `test_mechanism_algorithms.jl`

there was this, which looks like a typo in the arguments:

```
Jv_to_q̇_j = RigidBodyDynamics.velocity_to_configuration_derivative_jacobian(joint, qj)
Jq̇_to_v_j = RigidBodyDynamics.configuration_derivative_to_velocity_jacobian(joint, qj)
```