Using only these supplies, which question can Betty investigate with an experiment?
Does a catapult with a longer arm launch a rubber ball farther than a catapult with a shorter arm? Does a rubber ball travel farther when launched from a metal catapult or from a wooden catapult? Does a heavier ball travel farther than a lighter ball when launched from a catapult?
Betty visits a museum about ancient Greece. She notices an exhibit with models of wooden catapults that were used to launch large rocks across battlefields. She wonders what factors affect how far a catapult can launch an object. So, she decides to design an experiment. She has the following supplies available:
a wooden catapult with a 10-inch-long arm
a wooden catapult with a five-inch-long arm
two identical rubber balls
Experiments can be designed to answer specific questions. When designing an experiment, you must identify the supplies that are necessary to answer your question. In order to do this, you need to figure out what will be tested and what will be measured during the experiment.
Imagine that you are wondering if plants grow to different heights when planted in different types of soil. How might you decide what supplies are necessary to conduct this experiment?
First, you need to identify the part of the experiment that will be tested, which is the independent variable. This is usually the part of the experiment that is different or changed. In this case, you would like to know how plants grow in different types of soil. So, you must have different types of soil available.
Next, you need to identify the part of the experiment that will be measured or observed, which is the dependent variable. In this experiment, you would like to know if some plants grow taller than others. So, you must be able to compare the plants' heights. To do this, you can observe which plants are taller by looking at them, or you can measure their exact heights with a meterstick.
So, if you have different types of soil and can observe or measure the heights of your plants, then you have the supplies you need to investigate your question with an experiment!