Question 165 of 210

An inclined plane making an angle of $30^{\circ}$ with the horizontal is placed in a uniform horizontal electric field $200\dfrac{N}{C}$ as shown in the figure. A body of mass $1kg$ and charge $5mC$ is allowed to slide down from rest at a height of $1m$. If the coefficient of friction is $0.2,$ find the time taken by the body to reach the bottom.
$\left[g=9.8m{s}^{-2};\sin 30^{\circ}=\dfrac{1}{2};\cos 30^{\circ}=\dfrac{\sqrt{3}}{2}\right]$

A$0.92s$B$1.3s$C$0.46s$D$2.3s$

Show answer and solution▾

Answer: (B) $1.3s$

here $N=9.8\cos 30+1\sin 30\approx 9N$
so$a=\dfrac{9.8\sin 30-1\cos 30-\mu N}{1}$
$a=2.233m{s}^{-2}$
By $S=ut+\dfrac{1}{2}a{t}^{2}$
$=\dfrac{1}{2}\left(2.233\right){t}^{2}$
$\sin 30^{\circ}$
$t\approx 1.3\sec$