Basic Thermodynamics ~ J. Pohl © | www.THERMOspokenhere.com () - () |
The Bulgarian, Ivan Charakov, is shown moments before "ascent" of a back squat. The back squat consists of taking the load from the rack, descent to squatted position then ascent to full upright. A typical "ascent" required two seconds with the elevation of the bar increasing about one meter. Once, Ivan (in the 90kg class) did three repetitions of this lift with the bar set at 330kg.
Analysis to proceed past our event scenario "single-completed ascent" requires selection of a system. A number are apparent; none are "wrong." The system might be the weight - (W), Ivan - (I), or Ivan and the weight, (I+W) taken together.
An event and system defined, the next considerations are system properties/charateristics: mass, force, momentum, work, and energy aspects.
Weights as System ~ Momentum Analysis: The schematic (below right) shows the Barbell In its initial and final positions.
![]() | (1) This is Newton's 2nd Law written to express momentum, explicitly. |
Of course, the mass is constant. Hence left-of-Equality reduces as show below. Also there are two relevant forces; gravity and the supporting force by Ivan.
![]() |
(2)
This is the "f = m A" form written as "m A = ΣF" and with acceleration written as dV/dt. |
Ivan supports the barbell. The event might be called, permanence or static equilibrium. Suppose Ivan holds the weight for 5 seconds. Let's look at 3 seconds of time within that 5 second duration. Steps to proceed are. Specify the gravity force as mass times Earth-surface acceleration directed, (-K). Next separate variables, apply integration operator with limits to obtain:
![]() | (3)Permanence or static equilibrium |
Above left integrates promptly to equal zero. With that step, the Momentum Equation for a BODY [(1) ~ Newton's 2'nd Law] is reduced to (4) (below left).
![]() | (3)Permanence or static equilibrium |
An equation has an unknown quantity (or quantity it prescribes), in this case the force required of Ivan is determined (below right).
![]() | (4)(4) |
Summary: This "answer" was known from the start. However, the steps were effected to show a solution pattern.
System: Barbell (BB) Momentum Analysis ~ Lift: The sketch (right) is a scenario of a lift. Again we take the barbell as our system. We model it as a BODY (or point mass). The 2'nd Law conclusions for "event is lift" are the same as "support as event" (above). Newton's 2'nd Law, we learn, perceives no differentiation in the obviously different events, "shouldering" and "lifting." By retro-inspection, observe that the equations (Eqn-1 to 5) for just holding the weight are the the same as for the weight being lifted. Yet the events are different. More than Newton's 2'nd Law is needed. The 2'nd Law perceives no difference of the "weight lifted" and the "weight shouldered."
is different from the squat.
Work, a new idea is the answer.
The Bulgarian, Ivan Charakov, is shown in the "squat stage" of a competition lift. Once he adjusts his stance, he will extend his legs to raise the weight to his full height.
Analysis using principles of physics make reality more understandable. Stated briefly, analysis addresses three physical properties: mass, momentum and energy.