A box with weight 27 N is on a rough horizontal surface. An external force F is
ID: 2036582 • Letter: A
Question
A box with weight 27 N is on a rough horizontal surface. An external force F is applied horizontally to the box. A normal force ans a friction force are also present, denoted by n and f. A force diagram, showing the four forces that act on the box, is shown in the figure. When force F equals 6.5 N, the box is in motion at constant velocity. The bix decelerates when force F is removed. The magnitude of the acceleration of the box is closest to:
a. 0.60 m/s2
b. 1.8 m/s2
c. 2.4 m/s2
d. zero
e. 1.2 m/s2
Explanation / Answer
Box is at constant velocity means acceleration is zero, which means
Net force = 0
Fnet = F - f = 0
F = f
F = uk*N
uk = F/N = 6.5/27 = 0.241 = coefficient of friction
Now when F is removed
Fnet = m*a = -f
a = -f/m = -uk*N/m
N = m*g
a = -uk*g
a = -0.241*9.81 = -2.36 m/sec^2
Correct option is C.
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