Question

2 Main Question Consider a block (which may or may not be moving) on a slope experiencing three forces as shown the diagram. The slope is at an angle of a 21° above the horizontal. The three forces are Fi, 1 and (with ing magnitudes F 150 bs., P140 lbs, and F 75 lbs. shown in the fiure a) Which force is gravity, which is the normal, and F1 what could the other force be? b) In the usual coordinates (e horizontal, y vertical), determine the net force in the r-direction. c) In the usual coordinates, determine the net force in the y-direction. net,y d) What is the magnitude and direction of the net force? (Hint: check to make sure this makes sense) Direction:

Answer 1

a) F1 is the gravity

normal Force will be F2 and

other Force will be F3

b) Fnet,x = F3*cos(alpha) - F2*sin(alpha) = (75*cos(21)) - (140*sin(21)) = 19.85 N

c) Fnet,y = F2*cos(alpha) + F3*sin(alpha) - F1 = (140*cos(21)) + (75*sin(21))- 150

Fnet,y = 7.58 N

D)

magnitude is Fnet = sqrt(19.85^2+7.58^2) = 21.25 N

direction is theta = tan^(-1)(7.58/19.85) = 20.9 deg = 21 deg (approx) i.e along the incline plane