Free fall
Section: Kinematics | Syllabus: Cambridge AS Level Physics 9702
Acceleration of Free Fall Free fall occurs when an object falls solely under the influence of gravity, with no air resistance. In a uniform gravitational field (like near the Earth's surface), all objects fall with the same constant acceleration.
Acceleration of Free Fall (g) The constant acceleration of an object falling in a vacuum. Value: g 9.81 m s^-2 Important In the absence of air resistance, the mass of the object does not affect its acceleration.
A feather and a hammer would fall at the same rate in a vacuum. Experiment: Determining g A common method to determine the acceleration of free fall (g) involves measuring the time it takes for an object to fall a known distance.
Electromagnet and Trapdoor Method An electromagnet holds a small steel ball at a measured height (h). Switching off the electromagnet starts an electronic timer and releases the ball. The ball falls and hits a trapdoor, which breaks a circuit and stops the timer.
The time (t) is recorded. Using s = ut + fractionat^2: Since u = 0, s = h, and a = g, the equation becomes: h = fractiongt^2 Rearranging for g: g = fraction Reducing Errors Measure the height (h) from the bottom of the ball to the top of the trapdoor to avoid systematic errors .
Repeat the timing at different heights and plot a graph of h against t^2. The gradient of the graph will be fractiong.
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