A student decides to move a box of books into her dormitory room by pulling on a
ID: 1361310 • Letter: A
Question
A student decides to move a box of books into her dormitory room by pulling on a rope attached to the box. She pulls with a force of 138 N at an angle of 29.0° above the horizontal. The box has a mass of 22.0 kg, and the coefficient of kinetic friction between box and floor is 0.300.
(a) Find the acceleration of the box.
m/s2
(b) The student now starts moving the box up a 10.0° incline, keeping her 138 N force directed at 29.0° above the line of the incline. If the coefficient of friction is unchanged, what is the new acceleration of the box?
m/s2, up the incline
Explanation / Answer
horizantal force = Fx = F*cos37
vertical force N = m*g - F*sin37
frictional force fk = -ukN = uk*(m*g*cos29
net force = Fx + Wf
net force = m*a
F*cos29 - uk*m*g = m*a
138*cos29 - 0.3*22*9.8*cos29 = 22*a
a = 2.91 m/s^2
++++++++++
(b)
Fnet = F*cos29 - fk = ma
fk = uk*N = uk*(m*g - Fsin29)
a = 2.91 m/s^2
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