Question

A block of mass $10kg$ is released on a fixed wedge inside a cart which is moved with constant velocity $10m{s}^{-1}$ towards right. There is no relative motion between block and cart. Then work done by normal reaction on block in two seconds from ground frame will be $(g=10m{s}^{-2})$:

• A. $1320J$
• B. $960J$
• C. $1200J$
• D. $240J$

Answer 1

The correct option is B $960J$

Constant velocity means net force $=0$
Using Lami's theorem in the figure,
We have,

$\frac{N}{sin({180}^o-{53}^o)}=\frac{100}{sin{90}^o}$

$\therefore N=100sin{53}^o=80N$

Now, $W_N=NScos{53}^o$

$=\left(80\right)\left(20\right)\left(0.6\right)$

$=960J$