Load = 200 N. Effort force? A2: 50 N (200 ÷ 4 = 50)
Does a fixed pulley reduce the force needed? A2: No. It changes the direction of force, not the magnitude. student exploration pulley lab answer key
To raise the load 1 meter, how far must you pull the rope? A3: 2 meters (distance doubles) Load = 200 N
To lift load 0.5 m, how much rope do you pull? A3: 2.0 m (0.5 × MA) A2: No
Use this answer key to check your work, but more importantly, understand why the numbers appear as they do. Physics isn’t just about getting the right answer—it’s about predicting the trade-offs.
Why is actual MA always less than ideal MA? A: Friction in the pulleys and rope stiffness reduce efficiency.
True or false – Adding more pulleys always increases efficiency. A4: False – Mechanical advantage increases, but friction increases, reducing efficiency. Key Concept: Compound pulleys multiply force but sacrifice distance and add friction. Comparison Table (Quick Answer Key Reference) | Pulley Type | MA (Ideal) | Effort for 100N Load | Pull distance for 1m lift | Force direction change? | |----------------------|------------|----------------------|----------------------------|--------------------------| | Single fixed | 1 | 100 N | 1 m | Yes | | Single movable | 2 | 50 N | 2 m | No (still up) | | Compound (2 pulleys) | 4 | 25 N | 4 m | Yes | | Compound (3 pulleys) | 6 | ~16.7 N | 6 m | Yes | Sample Calculation Questions (With Answers) Q: A pulley system has an actual MA of 3.5 and an ideal MA of 4. If you lift a 140 N load, what is the actual effort force? A: Actual MA = Load ÷ Actual Effort → 3.5 = 140 N ÷ Effort → Effort = 140 ÷ 3.5 = 40 N