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Solid brick with variable mass and size

**Library:**Body Elements / Variable Mass

The Variable Brick Solid block adds to the attached frame a solid brick
with variable mass and size. The mass and side lengths (*x*,
*y*, and *z*) of the brick can each be a constant
or vary with time. A variable quantity can be specified directly as a physical signal or
it can be calculated as a function of the remaining quantities. Only one quantity,
either mass or one side length, can be calculated during simulation.

A reference frame encodes the position and orientation of the solid in a model. The
frame origin is located at the midpoint of the *x*- and
*y*-dimensions and at the lower end of the
*z*-dimension. These relationships are preserved during simulation. The
*z*-dimension increases asymmetrically relative to the lower
*z*-plane, along the positive direction of the
*z*-axis.

**Variable Brick with z-Dimension Calculated from Mass**

Visualization is dynamic. Solid dimensions update continuously as they occur, in the
visualization pane of **Mechanics Explorer**. The initial dimensions of
the solid depend on the parameters and physical signals that you specify. It is possible
for a variable dimension to begin with a zero value—for example, if it derives from a
physical signal whose initial value is zero also.

Density can itself be constant or variable. This quantity is specified as a constant if at least one solid parameter is calculated during simulation. It is calculated as a variable if all solid parameters are explicitly specified, either as (constant) block parameters or as physical signals. As in the case of the Solid block, you can specify a negative density, for example, to model voids in compound bodies.

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