Independent, dependent and control variables, hypotheses, choosing apparatus, risk, and writing a 6-mark plan.
What you will learn
- Name the independent, dependent and control variables
- Choose apparatus with the right range and resolution
- Match a hazard to a precaution
- Write a method someone else could follow
Three kinds of variable
- Independent: the one you change on purpose. It goes on the x-axis.
- Dependent: the one you measure. It goes on the y-axis.
- Control: everything else that could change the result. Keep each one the same, so the test is fair (valid).
A hypothesis is an idea about how one variable affects another that an experiment can test: "the longer the pendulum, the longer each swing takes".
- A student times a toy car down a ramp at different angles
- Independent: the angle of the ramp
- Dependent: the time to reach the bottom
- Control: the ramp length, the car, the starting point
A control variable is not the thing you measure. If the answer is "the time", it is almost never a control variable.
The rest of this lesson and its 7 practice questions are locked.
In this lesson
- Three kinds of variable
- Apparatus and risk
- Writing a 6-mark plan
7 practice questions, marked as you go; about 25 minutes in all.
Key terms
Hypothesis, Hazard, Harm
In this unit: Required practicals, maths skills and the equations
The skills every physics paper tests: units and standard form, uncertainty and errors, planning, graphs, the equations and the required practicals side by side.
- Units, prefixes and standard form
- Measurements, uncertainty and errors
- Variables, planning and risk
- Graphs: gradients, intercepts and areas
- The equations: learn, choose and rearrange
- The required practicals side by side
- Equation list B: recall and the formulae sheet
- Equation list C: word equations, recall and the equation sheet