Question

2) A person pulls a bucket of water up from a well with a rope. Assume the initial and final speeds of the bucket are zero (v-vr-0), and that the person lifted the bucket a vertical distance h. By looking at energy changes in the bucket-Earth physical system, we can make sense of the force the person must exert to pull the bucket up and the amount of work the person does. a) Think about whether this is an open or closed system. What energy systems undergo a change during the process? Construct a particular energy-system diagram for this process and include the algebraic expression of energy conservation (in terms of AE's and if open, any Heat or Work). solve algebraically for the work done by the person on the rope/bucket. Summary) to find the average force exerted by the person on the rope and bucket while they are b) Substitute the algebraic expression we use for the change in gravitational potential energy and c) Use the definition of work in terms of force and distance (refer to the Energy-Interaction Model lifting it up.

Answer 1

(a) you can draw the diagram by yourself. Notice that initially, the potential energy was zero, as the men pulls the bucket, the potential energy increases. The work done will be equal to change in potential energy

(b) work done by person = final potential energy - initial potential energy

work done = mgh_final- mgh_initial

work done = mgh

where m is mass, g is 9.8 m/s2 and h is vertical height

(c) Now, average force exerted by person on rope and bucket is given as

work = force * distance

force = work / distance

force = weight of bucket.