Question

In the figure shown, the blocks are of equal mass. The pulley is fixed. In the position shown, $A$ moves down with a speed $u$ and $v_B$ is the velocity of block $B$ in horizontal direction. Then:

• A. $B$ will never lose contact with the ground.
• B. The downward acceleration of $A$ is equal in magnitude to the horizontal acceleration of $B$.
• C. $v_B=u\cos \theta$
• D. $v_B=\frac{u}{\cos \theta }$

Answer 1

The correct option is C $v_B=u\cos \theta$

Let the velocity of the block B be $v_b$ along horizontal

The speed of the rope is $u$ along the axis joining block and pulley

Taking the horizontal component of speed $u$ of rope along horizontal, we get $ucos\theta$=$v_b$