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4. Gravity and Freefall

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In this mini-lecture, we explore gravity and freefall. In particular, we consider: (i) the universality of freefall, i.e. the fact that all objects fall with the same acceleration under gravity, no matter their mass, shape, or composition; (ii) Galileo’s explanation for the universality of freefall; (iii) dropping a hammer and a feather on the moon, an experiment actually done in 1971; and (iv) the concept of inertia and how this helps us understand why all objects, regardless of mass, fall at the same acceleration.


In this course, Professor Derek Raine (University of Leicester) explores kinematics, which is the motion of objects without considering the forces that cause them to move. In the first mini-lecture, we discuss speed and velocity, looking in particular at average speed and graphical representations. In the second mini-lecture, we turn towards acceleration, where we seek to understand the rate at which objects fall under gravity and derive useful equations for systems experiencing constant acceleration. The third mini-lecture includes a discussion of graphical representations of distance, speed, and time, followed by an example that ties together the concepts learned so far. In the fourth mini-lecture, we explore gravity and seek to understand why all bodies, regardless of mass, fall with the same acceleration under gravity (the universality of freefall). In the fifth mini-lecture, we introduce projectile motion, which is the motion of a projected object that moves along a curved path under the action of gravity only.


Derek Raine is an Emeritus Professor of Physics and Astronomy at the University of Leicester. His research has ranged over Relativity, Cosmology, General Relativistic Quantum Field Theory, Astrophysics, Biophysics, and education. Professor Raine was involved with the University of Leicester’s Scholarship of Teaching & Learning (SoTL) research where he developed alternative approaches to teaching, including computer simulations, problem-based and research-based learning, flipped learning, and spaced repetition.

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APA style

Raine, D. (2022, January 13). Kinematics - Gravity and Freefall [Video]. MASSOLIT.

MLA style

Raine, Derek. "Kinematics – Gravity and Freefall." MASSOLIT, uploaded by MASSOLIT, 13 Jan 2022,

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