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mechanics
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A diagram with labeled vector illustrations. Panel A shows vector addition with two green arrows A and B forming a parallelogram, and their sum C as a red diagonal. Panel B shows vector subtraction, with A and negative B forming resultant D. Panel C demonstrates vector components using angles and projections. Panel D uses the right-hand rule with thumbs to show the direction of the cross product E = A x B and its opposite, -E = B x A.
How rockets work: Newton's third law of motion explained
Two elephants pull a log in opposite directions with equal force, keeping the log stationary to illustrate Newton's law that balanced forces result in no movement.
Newton's law of gravitation: Apollo 15 gravitation experiment
Two diagrams compare a mass attached between two horizontal springs. In A, the mass m is centered and springs are at rest. In B, the mass is shifted right by distance x, stretching the left spring and compressing the right. A graph of the function x equals A cosine omega t, showing a cosine wave oscillating between A and negative A along the vertical axis, with horizontal axis marked at pi and 2 pi. A graph showing damped oscillations, with a red wave decreasing in amplitude over time. The vertical axis is labeled amplitude and the horizontal axis is labeled time. Dashed green lines illustrate the exponential decay envelope. Two graphs compare projectile motion. Panel A shows a parabolic path starting high on the Z axis and curving downward to the X axis. Panel B shows a parabolic path starting at the origin, rising upward, then curving back down to the X axis, illustrating an initial upward velocity. A diagram of a simple pendulum showing a mass labeled M suspended by a string of length L from a fixed point, with the pendulum displaced at an angle theta from the vertical and an arc indicating its swing path. A geometric diagram of a circular segment with radius labeled L, central angle labeled theta, arc length marked as L times theta, and a vertical segment inside labeled L times sine theta.
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Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.
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Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.
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A diagram with labeled vector illustrations. Panel A shows vector addition with two green arrows A and B forming a parallelogram, and their sum C as a red diagonal. Panel B shows vector subtraction, with A and negative B forming resultant D. Panel C demonstrates vector components using angles and projections. Panel D uses the right-hand rule with thumbs to show the direction of the cross product E = A x B and its opposite, -E = B x A.
vector mathematics Figure 1: (A) The vector sum C = A + B = B + A. (B) The vector difference A + (−B) = A − B = D. (C, left) A cos θ is the component of A along B and (right) B cos θ is the component of B along A. (D, left) The right-hand rule used to find the direction of E = A × B and (right) the right-hand rule used to find the direction of −E = B × A.

mechanics

physics
Written by
David L. Goodstein
Vice Provost and Professor of Physics and Applied Physics, California Institute of Technology, Pasadena. Coauthor of The Mechanical Universe and others.
David L. Goodstein
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Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
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mechanics, science concerned with the motion of bodies under the action of forces, including the special case in which a body remains at rest. Of first concern in the problem of motion are the forces that bodies exert on one another. This leads to the study of such topics as gravity, electricity, and magnetism, according to the nature of the forces involved. Given the forces, one can seek the manner in which bodies move under...

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