Q. A block of mass 5 kg, resting on a horizontal surface, is connected by a cord, passing over a light frictionless pulley to a hanging block of mass 5 kg. The coefficient of kinetic friction between the block and the surface is 0.5. Tension in the cord is [Take $g = 9.8\ ms^{- 2}$]
A) 49 N
B) 36 N
C) 36.75 N
D) 2.45 N
Explanation
(c) Refer to the free body diagram of block $B$
$5g - T = 5a$ or $T = 5g - 5a$
Refer to the free body diagram of block $A$
[image:5_image169.emf]
$T - f = 5a$
or $5g - 5a - 0.5 \times 5 \times g = 5a$
or 10$a = 2.5g = 2.5 \times 9.8$
or $a = 0.25 \times 9.8\ ms^{- 2} = 2.45\ ms^{- 2}$
Again, $T = (5 \times 9.8 - 5 \times 2.45)$N
$= (49 - 12.5)$ N=36.75 N
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.