A 20 kg block is pushed horizontally by 90 N. Coefficients μₛ=0.4 and μₖ=0.3, g=10 m/s². If friction magnitude is 10x N, find x.
Physics · Mixed Chapter
JEE Main Practice

Question

A 20 kg block is pushed horizontally by 90 N. Coefficients μₛ=0.4 and μₖ=0.3, g=10 m/s². If friction magnitude is 10x N, find x.

G1 Physics · Accepted Answer

Step 1: Normal reaction N=mg=20×10=200 N. Step 2: Maximum static friction fₛmax=μₛN=0.4×200=80 N. Step 3: Since applied force 90>80 N, block moves; kinetic friction fₖ=μₖN=0.3×200=60 N. Step 4: 10x=60⇒x=6.