Blocks A and B of masses l9 kg and 15 kg, respectively, are connected by a rope,
ID: 1313616 • Letter: B
Question
Blocks A and B of masses l9 kg and 15 kg, respectively, are connected by a rope, which passes over a light frictionless pulley, as shown. The horizontal surface is rough. The coefficients of static and kinetic friction are 0.40 and 0.20, respectively. External forces P and Q act on block B, as shown. In Fig. 5.9, force P equals 60 N. The maximum value of force Q, for which the system remains at rest is closest to: 220 N 240 N 190 N 230 N 270 N A man push s against a rigid, immovable wall. Which of the following is the most accurate statement concerning this situation? The man cannot be in equilibrium since he is exerting a net force on the wall. The man can never exert a force on the wall that exceeds his weight. The friction force on the man's feet is directed to the left. If the man pushes on the wall with a force of 200 N, we can be sure that the wall is pushing back with a force of exactly 200 N on him. Since the wall cannot move, it cannot exert any force on the man.Explanation / Answer
So let's first start by drawing a FBD (Free-body diagram) to find the net force acting on the weight. Next we use trig to determine the composite forces that go into the 8N at 62 degrees. This gives us 5.9N in the positive y-axis and 5.3N in the negative x-axis. So here we find that we have a net force of 3.7N in the positive x-axis and 5.9N in the positive y-axis. Now we have to find the composite of these forces! More trig... we use the pythagorean thereom to find the square root of the square sum of the sides (a2 + b2 = c2) which gives us (lets call it) 7N. Then we use Net force = (m)(a)
7N= (3.0)(a)
a=2.33333
which is a little off from B due to our rounding in our trig, but therefore the answer is B