Question

when designing an experiment we need to decide what things we will change, measure, and hold constant.
lets apply this idea to our boat race...
how can we plan an investigation to see how changing the mass affects the speed?
which variable should we change as our independent variable?
type of surface
fan force
total mass
cart speed
which variable should we measure as our dependent variable?
type of surface
fan force
total mass
cart speed
which variables should we keep the same as our controls?
type of surface
these are called independent variables, dependent variables, and controls.

Explanation:

• Independent variable: The variable that is changed in an experiment. In the boat - race experiment about how mass affects speed, we are interested in changing the mass. So, the independent variable is the one we change to observe its effect on another variable.
• Dependent variable: The variable that is measured and is expected to change as a result of the change in the independent variable. Since we want to see how mass (independent variable) affects speed, speed is what we measure (dependent variable).
• Controlled variables: Variables that are kept the same to ensure a fair experiment. The type of surface can affect the motion of the boat (e.g., a rough surface may cause more friction). To isolate the effect of mass on speed, the type of surface should be kept constant.

Answer:

• Independent variable: Total Mass
• Dependent variable: Cart Speed
• Controlled variable: Type of surface