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HOOKE’SLAW INVESTIGATION Lab report : variables, tables and graphs LEARNING OBJECTIVES We are learning to:Identify variables and use them to make a table and plot a graph What I’m looking for:You must be able to draw a simple table to record the results of an experiment (grade E) You should be able to identify the control, independent and dependent variables in an experiment (grade C) You could be able to plot a line graph of your results (grade B) VARIABLES Variables – these are all the factors that could have an effect on the investigation Control variables – these are the most important variables that should be considered, they usually need to be controlled (kept constant) to have fair test Independent variable – this the ‘input factor’ you will be changing and testing Dependant variable – this is the variable you measure that depends on the independent variable. CHECK YOUR LEARNING: 1 Complete Task 1 on your worksheet: Using 2 different colours, highlight the independent and the dependent variables in the 9 investigation aims listed. BASIC THEORY OF HOOKE’S LAW When a force is exerted on a spring it will either compress (push the spring together) or stretch the spring if the weight is hung on it. INVESTIGATION An investigation into how the amount of mass affects the extension of a spring In this experiment the extension of the spring is measured with increasing weights being added 1N, 2N, 3N to 5N. The extension is a measure of how much the spring stretched. (Not the total length of the spring) Independent variable Mass (g) going up in 100 grams Dependent variable Extension (cm) Control variable Forcemeter, spring, same set of masses. HOW TO DRAW A GOOD TABLE 1. Always use squared or ruled paper 2. Always use a ruler 3. The independent variable goes in the first column 4. The dependent variable goes in the next column 5. Always have 3 repeat columns or tables 6. Always have an average 7. Always round up your results (more on this soon!) RESULTS OF EXPERIMENTS Mass in g 100 200 300 400 500 extension of spring (cm) Try 1 extension of spring (cm) Try 2 extension of spring (cm) Try 3 Average extension of spring (cm) RESULTS OF EXPERIMENTS Mass in g extension of spring (cm) Try 1 extension of spring (cm) Try 2 extension of spring (cm) Try 2 Average extension of spring (cm) 100 4 5 3 4 200 8 7 9 8 300 12 12 12 12 400 16 15 17 16 500 20 19 22 20 HOW TO PLOT A GOOD GRAPH 1. Always use graph paper 2. Always use a sharp pencil 3. Make certain that the independent variable is on the x axis and the dependent variable is on the y axis 4. Have a suitable scale that fills the whole paper 5. Plot carefully putting an ‘x’ at each point 6. Do not join the points together using a ruler. Add a straight line or a smooth curve that is the best fit showing the pattern of your results. A graph to show how a spring's length changes with mass 18 extension of a spring cm 16 14 12 10 8 6 4 2 0 100 200 300 mass in g 400