- #1

shaggyace

- 11

- 0

## Homework Statement

A 1.8 kg rock is released from rest at the surface of a pond 1.8 m deep. As the rock falls, a constant upward force of 4.3 N is exerted on it by water resistance. Let y=0 be at the bottom of the pond.

Calculate the nonconservative work, W nc, done by water resistance on the rock, the gravitational potential energy of the system, U, the kinetic energy of the rock, K , and the total mechanical energy of the system, E , when the depth of the rock below the water's surface is 0 .

## Homework Equations

W=Fd

K=0.5(mv)^2

U=mgd

E=U+K

Wnc=ΔE=Ef-Ei

## The Attempt at a Solution

I've been going at this one for almost an hour now. I tried finding the final velocity of the rock first since it starts from rest so that I can find its kinetic energy. To find its non conservative work done by water resistance, I used the Work =force *distance formula and multiplied the force of the water resistance by 1.8 m, but that doesn't seem right. To find its gravitational potential energy, I used the U=mgd formula but got the wrong answer for some reason. For the kinetic energy, I used K=0.5(mv)^2 and used the velocity from the first calculation. To find the total mechanical energy, I added up the potential and kinetic energies. Did I do something wrong? Someone please help me.