Answer the following questions about friction. 12 lb 13 lb 14 lb 20 lb For the f
ID: 1882975 • Letter: A
Question
Answer the following questions about friction.
12 lb
13 lb
14 lb
20 lb
For the figure in part A, P=15 lb, W = 20 lb, and Q = 0, the value of the friction force is:
12 lb
14 lb
15 lb
20 lb
For the figure in part A, W = 20 lb, and Q = 20 lb, the maximum the friction force can be is:
12 lb
14 lb
24 lb
28 lb
The direction of the friction force is:
1- in the direction of impending motion
2- oppoisite the direction of impending motion
3- perpendicular to impending motion
4- always horizontal
W
W+Pcos
W+Psin
W-Pcos
W-Psin
A.For P=13 lb, W = 20 lb, and Q = 0, the value of the friction force is:
12 lb
13 lb
14 lb
20 lb
Explanation / Answer
here,
A)
the static friction force , Fs = us * (Q + W)
Fs = 0.7 * ( 20 + 0) = 14 lb
as Fs > P
the frictional force = P = 13 lb
B)
the static friction force , Fs = us * (Q + W)
Fs = 0.7 * ( 20 + 0) = 14 lb
as Fs < P
the frictional force = 14 lb
C)
the maximum friction force , Fs = us * (Q + W)
Fs = 0.7 * ( 20 + 20 ) = 28 lb
d)
the direction of friction force is 2) opposite to the direction of impending motion
e)
equating the forces vertically
the normal force ,N = W - P * sin(theta)