Work and refrigerator energy

[glasshut137]

Homework Statement

A mover's dolly is used to deliver a refrigerator up a ramp into a house. The refrigerator has a mass of 110 kg. The ramp is 2.1 m long and rises 0.42 m. THe mover pulls the dolly with constant velocity and with a steady force of 445 N up the ramp. The dolly and ramp constitute a machine. g=9.81/s^2

What work does the mover do?


The attempt at a solution

well i thought that this was a simple question. I used W=F*x using 445 N as F and 2.14 M as x which i got from using the pythagorean theorem. My final answer was 953.007 J but it was incorrect. Can someone help me understand what I'm doing wrong?

 

[HallsofIvy]

You are told that the ramp is 2.1 m long. The ramp is not lying on the ground! The ramp is the hypotenuse of the right triangle. Looks to me like you should just have 445*2.1!

 

[Moetasim]

Your approach is correct, but there are a few things to consider. First, make sure you are using the correct value for the height of the ramp. The given height of 0.42 m is the vertical height, but you need to use the length of the ramp (2.1 m) as the distance. This is because the work done by the mover is in the direction of the ramp, not just the vertical direction.

Secondly, make sure you are using the correct value for the force. The problem states that the mover pulls with a steady force of 445 N, but this is not the same as the weight of the refrigerator (110 kg * 9.81 m/s^2 = 1079.1 N). The force of 445 N is the net force needed to overcome the force of gravity and move the refrigerator up the ramp with constant velocity. So, your calculation should be W = 445 N * 2.1 m = 934.5 J.

Lastly, make sure you are using the correct units. The work done should be in joules (J), not newtons (N). So, your final answer should be 934.5 J.

In summary, the work done by the mover to move the refrigerator up the ramp is 934.5 J. This work is equal to the force applied (445 N) multiplied by the distance moved (2.1 m), in the direction of the ramp.