Ql2 & Free-Response Question, Afternoon Section (B) You drag a box of mass M acr
ID: 1779367 • Letter: Q
Question
Ql2 & Free-Response Question, Afternoon Section (B) You drag a box of mass M across a horizontal floor by pulling with force of magnitude F at an angle above the horizontal. There is friction between the ground and the box, and the box moves with constant velocity a distance D across the floor. FCUs (a) In the time it takes the box to travel distance D, what is the work done on the box from the applied force F? (5 points) ) In the time it takes the box to travel distance D, what is the work done on the box from the normal force? (5 points) (c) What is the coefficient of kinetic friction between the floor and the box? (5 points)Explanation / Answer
(a) W = F.d = F d cos(theta)
W = F D cos(theta)
(b) W = N . D cos90 = 0
(c) in horizontal,
Fnet = F cos(theta) - f = 0
f = F cos(theta)
in vertical, Fnet = N+ F sin(theta) - m g = 0
N = M g - F sin(theta)
f = u N
F cos(theta) - u M g + u F sin(theta) = 0
u = F cos(theta) / ( M g - F sin(theta))