Newton’s Laws suggest that any change in direction is the result of a force having sufficient magnitude to effect such a change. Now we’re getting somewhere, and it’s about me! Time for a Change. Intuitively, this should translate into how much time it takes to stop – how quickly the kinetic energy is absorbed or dissipated. If I hit an airbag, call it a stunt if I hit concrete pavement, call that messy. Where are we headed with all of this?īack to my falling body example: think of impact in terms of what stops my fall. In this equation, mass (m) refers to inertial mass or a proportionality factor relative to an object’s tendency to resist changes in motion. Momentum isn’t a force per se it’s a product, but it can be related to Newton’s Second Law and therefore to inertia. This can be similarly expressed in terms of momentum (P) = mass (m) x velocity at impact (v), therefore P= 10.2 N(4.4m/sec) = 44.9 Kg If I weigh 100 Kg and that weight is the product of my mass times gravity, then I have a mass of 10.2 Kg and with the help of gravity, I exert a force of 10.2Kg x 9.8 m/sec2 =10.2*9.8 Kg A Newton (N) is the force exerted by gravity on an object with mass (m). Kinetic energy is measured in Joules – the work expended by applying a force of 1 Newton (or 1 Kg Hold that thought…Į k=1/2mv 2 is a simple formula for kinetic energy. Timing is everything – if I can stop my falling body over a less sudden time span of a few seconds, then the stop at the end becomes less critical and certainly less messy. It’s not the fall that matters, but the sudden stop at the end. What’s more important is not so much that an object changes direction or that it stops, but rather how quickly it does so. However, if the direction of motion is not vertical, then we may not fully consider dynamic loads appropriately, mainly because gravity is less intuitive when motion isn’t vertical or down. We tend to think of dynamic loads in terms of a falling object, because it’s relatively easy to relate acceleration “a”, in F=ma, as the force of gravity. These are basic precepts of other formulas, which calculate kinetic energy, force of impact and energy dissipation. On the other hand, if an object is not accelerating (either at rest or at a constant velocity) then it has no force acting upon it. Simplified, if an object is accelerating, then it has a force applied to it. When an object accelerates or decelerates, its change in velocity over time is important, but F=ma considers only the instantaneous force of an object’s inertial mass relative to its time rate of change, when accelerating at a fixed rate. The acceleration component to this equation implies that time is a related factor indeed acceleration is the time rate of change in velocity. One of the most basic equations in physics is F=ma. Force is equal to mass times acceleration. In this equation, any change in values for mass or acceleration effects a proportional change in force. Shock loads, impact loads and vibrational loads can all be considered dynamic in nature, but are not the same. Newton’s Laws of Motion reconcile the equilibrium in static systems easily.įor the purposes of this article, you should consider that the term “dynamic load” refers to any load in motion, changing velocity or direction. Loads in a static system are constant and unchanging. In simple terms, a dynamic load is any load that moves, changing magnitude or direction over time.
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