1. You pull on a rope attached to a box with mass 30.0 kg. The rope is at a 30.0
ID: 1776626 • Letter: 1
Question
1. You pull on a rope attached to a box with mass 30.0 kg. The rope is at a 30.0 angle above the horizontal. You pull the box across a horizontal floor. The coefficients of friction are 0.326 and M0.213. You exert a force on the rope of 283 N and pull the box, which initially is at rest, 7.28 m across the floor a. How much work did you do? b. How much work did friction do? c. When the box reaches 7.28 m from the starting point, how much kinetic energy does it havei? d. If it took you 3.24 seconds to move the box 7.28 m, what average power were you exerting?Explanation / Answer
here,
mass , m = 30 kg
theta = 30 degree
us = 0.326
uk = 0.213
F = 283 N
s = 7.28 m
a)
the work done by you W1 = F * s * cos(theta)
W1 = 283 * 7.28 * cos(30) J
W1 = 1784.2 J
b)
the frictional force , ff = uk * ( m * g - F * sin(theta)
the work done by frictional force , W2 = ff * s * cos(180)
W2 = - 0.213 * ( 30 * 9.81 - 283 * sin(30)) J
W2 = 32.5 J
c)
the kinetic energy gained , KE = net work done
KE = W1 + W2
KE = 1784.2 - 32.5 J = 1751.7 J
d)
the average power , P = KE/t
P = 1751.7 /3.24 W
P = 540.7 W
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