Note: This page has been translated by MathWorks. Click here to see

To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

Solid brick with variable mass and size

**Library:**Simscape / Multibody / 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.