Longboard physics
A few (surprising?) thoughts on how the wheels on a longboard or skateboard actually move.
More details | Watch nowThe Longboard – speedometer
Jonathan describes his adventures with a longboard and some different methods of making a speedometer for it.
More details | Watch nowOscillations
Inertia and restoring forces can, with low friction or damping, lead to oscillations and resonance. We analyse the mechanics of vibrations.
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The inverse square law explains planetary motion - and apples falling. Newton's law, measuring G, calculating orbits.
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Torques produce angular acceleration, moment of inertia 'resists' it. Rotational kinetic energy and angular momentum.
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p=mv. If external forces are zero, momentum is conserved. In collisions, energy may be conserved (elastic) or not (inelastic).
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In finite objects, the total external force equals the total mass times the acceleration of a point called the centre of mass.
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The total work done on an object equals the increase in its kinetic energy. For conservative forces, we can define potential energy.
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Carefully distinguish mass and weight. Hooke's law quantifies deformation. Contact forces have normal and frictional components.
More details | Watch nowNewton’s laws of motion
F=ma (laws 1&2). Forces come in pairs that add to zero (3). Newton's laws apply in inertial frames of reference. Some common approximations made in applying them.
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In simple harmonic motion, displacement, velocity and acceleration vary sinusoidally with time, but with different phases.
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