Lifting the weight without a pulley requires a force of 400 N over a distance of 4 m. How do these values change when the pulley is applied?
When a pulley is used, it reduces the force needed to lift the weight. The force required to lift the weight with a pulley is equal to the weight of the object divided by the number of supporting ropes or cables attached to the pulley system.
If a single fixed pulley is used, the force required to lift the weight is the same as the weight of the object (400 N) but it is distributed between the two segments of the rope, so each segment will experience a force of 200 N.
The distance over which the force is applied will remain the same (4 m) because the weight still needs to be lifted that distance.
Therefore, when a pulley is applied, the force required to lift the weight decreases but the distance over which this force is applied remains the same.