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The physics of a little lifting


I graduating from Civil Engineering at the University of Alberta a few years ago.  My trip this past week brought back a lot of memories being on campus.  One of those was talking with the family about math.  My older brother was teaching Tyler (my 10year old nephew) about math and the times tables he's struggling a bit on and so forth.  It turned into a few days of quizzing everyone about real life applications of math and physics.  So I got on with big brother about weight training and how we go about lifting throughout the week.  Sometimes to maximize our amount of work over 10 minutes and heavy lifting.  So, if you were ever curious about what WORK is as it applies to our lifting and combatting gravity read on.  If you don't care.  I understand.

Work, Force, Energy and Power

1st off, there is always some confusion between these terms, and the units used to measure them. A force is an influence that causes a change in the motion of an object; in other words, acceleration. Work is the exertion of force to produce movement, while energy is the potential to do work, and is expended when work is done. For example, pushing or pulling a barbell in a certain direction involves applying a force, which does work, and energy must be used up. Work and energy can both be measured in joules.  Power is the rate at which energy is used and is measured in watts.  Keep in mind the amount of energy required to lift a small apple 1 meter against the earth's gravity is roughly equivalent to 1 Joule.

So...

Work = Force(N) x Distance (m) x Cosine angle of theta

 

Take an example like this -  A 60 kg (135lbs) bar must be moved 1.8 meters to catch the bar in a standing position.

60kg*9.81m/s^2 = 589 N Force.

 

So 589N*1.8m* cosine theta = 1060 Joules of work for standing position. **Let's assume cosine theta is 1 (it involves the horizontal distance from start to finish using cosine of the angle**

 

Now as a barbell gets heavier the lifter is going to try to reduce the amount of work that must be used in order to catch this bar.  

 

So we know the three positions a lifter can catch a barbell in.

There's a standing position and there's the power position (which is a small kind of a slight squat position) and then there’s the squat position.

 

Using the same bar and cleaning into a power position of say 1.6 meters instead of 1.8m

589N*1.6m* cosine theta = 942 J which reduces the amount of total work to 942 Joules versus a 1060 J for a full standing catch .

 

The squat position is the preferred position for the most maximum weights because it'll travel less distance. Say 1.3 meters

 

589N*1.3m* cosine theta = 766 J

It requires 766 joules of work versus the 1060 J for catching it standing.

 

So when your at your maximal weights a lifter is going to catch the barbell in the squat the position whether it's a snatch or a clean.