Usually, each weight plate is marked with a number. Some of these figures give the actual weight of the plate. However, some are not but the actual force you need to life the plate. On some machines, the number is just an index indicating the number of plates being lifted.
Next time before you push or pull the weight plate at the resistance machine, pay attention how the cable is connected to the weight stack – via pulley or just pure cable.
- If only cable is used, if the weight plate is 50 pounds, you will need 50 pounds of force to lift it.
- If a pulley is used, it will be difference case. A pulley (also called a sheave or block) is a wheel with a groove between two flanges around its circumference.
- In physics terms, pulleys are used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion.
- In layman term and in weight lifting machine context, with pulley, when you see a number indicating 50 pounds, you may not lift that amount of weight. The pulley has made the weight easier to be lifted as shown in the diagram below.
In this case above, the force required to lift the weight is the same.
In this case, because how the pulley system is designed, the force required is cut by half.
The next time you thought you are stronger with pulley resistance machine, do not get overjoyed as you may only half of the force.
Category: Weight Training
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