A box of mass 20 kg displacing along the positive x-axis is subjected to a push
ID: 1514083 • Letter: A
Question
A box of mass 20 kg displacing along the positive x-axis is subjected to a push force of 100 N, a pull force of 50 N (both horizontal and in the positive x-direction), and friction, for which the interface has a coefficient of kinetic friction of 0.2. Calculate the net force along the axis of displacement.
A. 11 N B. 47 N C. 111 N D. 150 N E. 39 N
If this net force in problem 4 acts for a time of 2.7 s, and the box was initially at rest, calculate the net work done during this time.
A. 111 J
B. 150 J
C. 39 J
D. 1500 J
E. 2220 J
Calculate the work done by friction from the above problem (4).
A. 150 J
B. -1110 J
C. 784 J
D. -150 J
E. -784 J
Explanation / Answer
frictional force fk = uk*m*g
net force Fnet = Fpush + Fpull - fk
Fnet = 100 + 50 - (0.2*20*9.8) = 111 N
option (c)
+++++++++++++++++++
acceleration a = Fnet/m = 111/20 = 5.55 m/s^2
displacement x = 0.5*a*t^2 = 0.5*5.55*2.7^2 = 20.2 m
work = Fnet*x = 111*20.23 = 2220 J
option E
+++++
Wf = fk*x = - uk*m*g*x = -784 J
option E
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.