Block B is placed on a smooth surface. Block A is placed on rough surface of block B with coefficient of friction 0.60. The mass of A and B are 2 kg and 4 kg respectively. Find the frictional force between A and B (in N)
Physics · Mixed Chapter
JEE Mains

Question

Block B is placed on a smooth surface. Block A is placed on rough surface of block B with coefficient of friction 0.60. The mass of A and B are 2 kg and 4 kg respectively. Find the frictional force between A and B (in N)

Physics · Mixed Chapter

G1 Physics · Accepted Answer

Step 1: External horizontal forces are 2 N to the right on A and 20 N to the left on B. Total mass is 2+4=6 kg, so common acceleration if no slip is a=(2−20)/6=−3 m s⁻² (take right positive). Step 2: For top block A, 2+f=mₐa=2×(−3)=−6; thus f=−8 N. Friction on A is 8 N to the left. Step 3: Maximum available static friction is μmₐg=0.6×2×10=12 N >8 N; no slipping occurs. Step 4: Actual friction magnitude is 8 N. Answer: 8.