A team of biomechanical engineers conducted an experiment to evaluate the impact attenuati… — ACT

A team of biomechanical engineers conducted an experiment to evaluate the impact attenuation of 3D-printed lattice structures used in protective athletic gear. In four separate trials, the engineers varied the strut angle of the elastomer lattice ( $30^\circ$ , $45^\circ$ , $60^\circ$ , and $75^\circ$ ) while holding the lattice density ( $0.25\text{ g/cm}^3$ ), polymer resin formulation, and drop impact height ( $2.0\text{ m}$ ) constant. In each trial, a drop tower released a mass onto the lattice sample, and the peak acceleration (measured in $g$ ) transmitted to an underlying sensor was recorded.

Match each experimental component from the investigation to its corresponding variable classification.

Strut angle of the elastomer lattice ( $30^\circ$ , $45^\circ$ , $60^\circ$ , $75^\circ$ )Independent Variable
Peak acceleration ( $g$ ) transmitted to the sensorDependent Variable
Drop impact height ( $2.0\text{ m}$ ) and lattice densityControlled Variable

Answer

Strut angle corresponds to the Independent Variable; Peak acceleration corresponds to the Dependent Variable; Drop impact height and lattice density correspond to Controlled Variables.

In experimental design, the independent variable is the parameter explicitly manipulated by the experimenters (the strut angle). The dependent variable is the observed outcome measured to assess the effect of that manipulation (the peak acceleration). Controlled variables are parameters deliberately kept uniform across all trials so they do not confound the results (drop height and lattice density).

Step-by-Step Solution

Identify the factor intentionally manipulated by the researchers across experimental trials.

The strut angle (

30^\circ

45^\circ

60^\circ

75^\circ

) is altered between trials.

The variable deliberately changed by the experimenter is the independent variable.

Identify the quantity measured to evaluate the effect of the manipulated factor.

The peak acceleration (

g

) transmitted to the sensor is measured after each impact.

The factor observed and measured to quantify the response is the dependent variable.

Identify the parameters kept constant throughout all trials.

The drop impact height (

2.0\text{ m}

) and lattice density (

0.25\text{ g/cm}^3

) remain unchanged across trials.

Factors kept unchanged to ensure that observed changes in the dependent variable are solely due to the independent variable are controlled variables.

Key Concept

Experimental Variable Classification (Independent, Dependent, and Controlled)

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