two boxes of mass m1 = 8 kg and m2 = 5 kg are touching and rest on a rough, hori
ID: 1777383 • Letter: T
Question
two boxes of mass m1 = 8 kg and m2 = 5 kg are touching and rest on a rough, horizontal floor. the kinetic coefficient of friction is 0.25 and the static coefficient of friction is 0.33.
a) if a force is applied to m1 so that it pushes m1 against m2 what value of force must be applied before both masses will move?
b) if a force of 50N is applied to both boxes what will be their acceleration?
c) what will be the force between the boxes?
d) How much kinetic energy will the two boxes have if this force is applied for a distance of 30 cm?
Explanation / Answer
Force of friction when both blocks move together = mus* ( m1+m2)*g = 0.33*13*9.81= 42.08 N ( ans)
Net friction force when 50 N is applied = muk*(m1+m2)*g = 0.25*13*9.81= 31.88N
Net force = 50-31.88 = 18.12 N
Acceleration= 18.12/(5+8) = 1.39 m/sec^2 ( ans)
Force between the box = m2*a= 5*1.39 = 6.95 N ( ans)
Kinetic energy = Work done by net force 18.12 N = 18.12 *0.3 = 5.44 J ( ans)
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