Question

Block $B$ has mass $m$ and is released from rest when it is on top of wedge $A$, which has a mass $3m$. Determine the tension in cord $CD$ needed to hold the wedge from moving while $B$ is sliding down $A$. Neglect friction.

• A. $2mg\cos \theta$
• B. $\frac{mg}{2}\cos \theta$
• C. $\frac{mg}{2}\sin 2\theta$
• D. $mg\sin 2\theta$

Answer 1

Answer: (C)

$T=N\sin \theta$ and $N=mg\cos \theta$
$T=mg\cos \theta \sin \theta =\frac{mg}{2}\sin 2\theta$