How Much Do Pulleys Reduce Weight

You d still have trouble but you might be able to do it because each pulley would lift half the weight or 1 000 pounds and a quarter of that weight is 250 pounds. This efficiency increases with really big loads 600 lbs and larger mechanical advantage such as 6 1 and 9 1.

Powerful Pulleys Lesson Teachengineering

Pulleys can also provide us with a mechanical advantage when we use several together and more rope.

How much do pulleys reduce weight. If you added a third pulley and a third person to the job however each person would only have to exert 167 pounds of force which is well within their ability so this system would work easily. Now you have a 100 pound weight which is more manageable. Now suppose if the applied effort raises the weight w and the pulley p1 by x meters in order to maintain tightness of the string attached to its axle and balance the movement pulley p2 has to move through a distance of 2x meters.

Pulleys can reduce the acceleration force required to lift an item but the total amount of work is the same. With a simple pulley the force you must exert is equal to the weight of the load. The 100kg mass 1000 newton weight is now effectively supported by two sections of the same rope the two strands on the left instead of just one ignoring the loose end of the rope you re pulling with and this means you can lift it by pulling with a force of just 500 newtons half as much.

That s why we say a pulley with two wheels and the rope wrapped around it this way gives a mechanical advantage me of two. Since 5th grade science i ve known that using a pulley reduces the weight of an item by 50 and adding another pulley with reduce another 50 etc. The effort force for a pulley with 4 ropes friction loss μ 0 8 and load 100 kg can be calculated as s 100 kg 9 81 m s2 0 8 4 307 n dynamics motion velocity and acceleration forces and torques.

Lets say you want to lift a 100 lb weight. You can actually move that weight. With a compound pulley two or more pulleys combined together you can reduce the force required to lift the load.

How do pulleys reduce the weight of an item. Pulley s can also change the direction of force allowing you to take advantage of the force of gravity to lift things upwards. Remember again that a pulley uses this concept of mechanical advantage to make work easier because it changes the way you re doing work.

Yes a double pulley definitely does come in handy. For example in a 1 1 haul you gain about 7 efficiency going from a 1 5 pulley to a 3 75 pulley. But a larger pulley has increased bulk weight more and cost.

The applied effort lifts the weight and also the entire pulley system under the topmost pulley. It is much easier to use the pulley because as long as we weigh more than 10 kilograms we can just hang onto the end of the rope and take advantage of gravity so our weight provides all the necessary force to lift the object.

Lecture18 Mechanics Summary