How do you think real pulley systems are different from ideal pulley systems, and how would that affect the mechanical advantage of real pulley systems?

Answer 1

Real pulley systems differ from ideal pulley systems in several key ways that affect their mechanical advantage. Here’s a breakdown of these differences and their implications:

1. Friction

• Ideal Pulley Systems: These systems assume that there is no friction between the pulley and the rope, as well as no internal friction in the pulley bearings.
• Real Pulley Systems: In practical situations, there is always some friction present, both at the axle of the pulley and between the rope and the pulley. This friction leads to energy loss, requiring more force to lift the load than in an ideal system.

Effect: The actual mechanical advantage (AMA) will be less than the theoretical mechanical advantage (TMA) because some of the input energy is lost to friction.

2. Mass of the Pulley

• Ideal Pulley Systems: Pulleys are considered massless, which means they do not require any force to move themselves.
• Real Pulley Systems: The pulleys have mass, which contributes to the overall force required to lift the load. The weight of the pulleys has to be overcome, which again decreases the mechanical advantage.

Effect: The presence of mass in the pulleys reduces the total mechanical advantage since part of the input force must be used to accelerate the pulleys themselves.

3. Rope Stretching

• Ideal Pulley Systems: It is assumed that the rope is inextensible, meaning it doesn't stretch when load is applied.
• Real Pulley Systems: Ropes have some degree of elasticity or stretch, which can absorb some of the force applied, leading to inefficiencies.

Effect: Stretching of the rope can lead to a delay in load movement, impacting the efficiency and responsiveness of the mechanical advantage.

4. Alignment and Rigidity

• Ideal Pulley Systems: The system is assumed to be perfectly aligned and rigid.
• Real Pulley Systems: Misalignment and flex in the supporting structures can lead to additional resistance when the system is in use.

Effect: Any misalignment can lead to increased forces required to lift the load, reducing the effective mechanical advantage.

Conclusion

In summary, the effective mechanical advantage of real pulley systems is affected by factors such as friction, the mass of the pulleys, rope elasticity, and system alignment. Because of these factors, the actual mechanical advantage will typically be less than the theoretical mechanical advantage calculated for an ideal pulley system. Understanding these differences can help in designing more efficient pulley systems and choosing suitable materials and configurations for real-world applications.