NEET2015PhysicsLaws of MotionActual
A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches 30 ° , the box starts to slip and slides 4 . 0   m down the plank in 4 . 0   s . The coefficients of static and kinetic friction between the box and the plank will be, respectively:
Options
- A0.6 and 0.5
- B0.5 and 0.6
- C0.4 and 0.3
- D0.6 and 0.6
Correct answer
A. 0.6 and 0.5
Step-by-step solution
μ s = tan ⁡ 30 o = 1 3 ⇒ μ s = 0.57 = 0.6 S = u t + 1 2 a t 2 4 = 1 2 a 4 2 ⇒ a = 1 2 = 0.5 a = g   s i n θ - μ k g c o s θ ⇒ μ K = 0.9 3 ≈ 0.5