Physical World Working as a Scientist Investigation Design
Energy Conversion Device Jean and Fintan designed and built an energy conversion device that transforms energy from one form to another to perform a function. The materials they used were:
z A large elastic band connected between two supporting columns (e.g. the legs of a laboratory chair) to create a catapult.
z A piece of cardboard taped to the middle of the elastic band. z A toy car held in the cardboard and pulled back different distances.
Toy car Lab floor
Catapult Supports
Fig. 16.5.1 The set-up
They wanted to see how the device worked to move the car across the laboratory floor. Your challenge is to advise them about how to carry out the task in a scientific way.
1 What are the dependent and independent variables in this investigation? 2 What would the controls be in this investigation?
Jean and Fintan pulled the car back in the elastic catapult a set number of distances and released it, allowing it to roll across the laboratory floor each time. They repeated this ten times, stretching the elastic by one centimetre more each time.
3 Describe the measurements Jean and Fintan would take in this investigation and the instruments they would use. How would they reduce errors? Which errors are random errors and which are systematic errors? How would you reduce both types of errors? Remember, scientists change only one variable at a time.
Jean and Fintan’s teacher reminded them that it is important to note any observations they made during the investigation and not just the measurements. She asked what they had noticed in terms of energy transfer when they pulled the catapult back and let the car go.
4 What useful energy transfers would the students have observed?
5 Would the students have observed any waste energy transfers? If so, what would they be?
6 Sketch a Sankey diagram of the energy transfers taking place in this investigation. Jean and Fintan collected the following table of data for this investigation:
