Block A in the figure weighs 1.01 N, and Block B weighs 3.80 N. The coefficient
ID: 1319566 • Letter: B
Question
Block A in the figure weighs 1.01 N, and Block B weighs 3.80 N. The coefficient of kinetic friction between all surfaces is 0.26.
Find the magnitude of the horizontal force F necessary to drag block B to the left at a constant speed if A and B are connected by a light, flexible cord passing around a fixed, frictionless pully.
I created the following force diagram:
Based on the above force diagram I got the following equation for the force F
However, the answer was incorrect. Would someone please be able to explain to me where I went wrong and how to correct my answer? Thank you.
Explanation / Answer
Net force on A = 0
T - mue*mA*g = 0
T = mue*mA*g
net force on B = 0
-F + T + mue*mA*g + mue*(mA+mB)*g = 0
F = T + mue*mA*g + mue*(mA+mB)*g
= mue*mA*g + mue*mA*g + mue*(mA+mB)*g
= 2*mue*mA*g + mue*(mA+mB)*g
= 2*mue*WA + mue*(wA+wB)
= 2*0.26*1.01 + 0.26*(1.01+3.8)
= 1.78 N