IB DP Physics(2025)A1.P1 Free Fall Practical: Measuring g

Free IB DP Physics hands-on practical for Topic A.1 Kinematics (SL and HL, first assessment 2025): measure the acceleration of free fall g by timing an object falling from rest through a range of heights, then linearise s = ½gt² and read g from the gradient of a graph of s against t². This complete, no-cost lab is the first free hands-on practical from the premium YPhysics IB DP Physics catalogue, so a teacher can see exactly what the paid packs deliver before buying one.

his is a structured IB Inquiry lab worksheet, not an expository lesson, built around the IB skills in the study of physics that it names explicitly. The worksheet runs the complete practical cycle. Students state and explain a prediction from s = ½gt², set out the independent, dependent and controlled variables, and justify the range of drop heights (about 0.20 m to 1.00 m) and the five repeat readings taken at each height. They address the safety hazards of a falling steel ball, a top-heavy clamp stand and the low-voltage electromagnet circuit, then collect repeat fall times on an electronic millisecond timer and record each measurement with its ± uncertainty.

In processing, students linearise the free-fall relationship: a graph of s against t² is a straight line through the origin whose gradient is g/2. They compute means and t² with propagated uncertainties (squaring a value doubles its fractional uncertainty), plot the points with horizontal error bars, draw the line of best fit, and read the gradient to obtain g. Lines of maximum and minimum gradient through the error bars fix the uncertainty in g. Students then state the relationship found, compare their value against the accepted 9.81 m s⁻², judge whether 9.81 m s⁻² lies within their uncertainty range, and evaluate the random and systematic errors: air resistance and release delay both lengthen the measured times and pull g low, while a zero error in the height shifts the intercept, not the gradient. Reaction time is deliberately excluded, because the electronic timer removes it. A Nature of Science note on graphical analysis shows how drawing one line through many readings turns a scatter of measurements into a single, evidence-based value.