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4-1.Newton's Laws of Motion
hard
For the given fig. find the speed of block $A$ when $\theta = {60^o}$
A
$2\sqrt 3 \,m/s$
B
$4\,m/s$
C
$2\,m/s$
D
None
Solution
$x^{2} y^{2}=\ell^{2}$
$2 \mathrm{x} \frac{\mathrm{dx}}{\mathrm{dt}}+2 \mathrm{y} \frac{\mathrm{dy}}{\mathrm{dt}}=2 \ell \frac{\mathrm{d} \ell}{\mathrm{dt}}$
$\mathrm{xU}_{\mathrm{x}}+\mathrm{yU}_{\mathrm{y}}=0$
$\mathrm{U}_{\mathrm{y}}=-\frac{\mathrm{x}}{\mathrm{y}} \mathrm{U}_{\mathrm{x}}$
$=-\tan \theta \mathrm{U}_{\mathrm{x}}=\tan 60 \times \mathrm{U}_{\mathrm{x}}$
Standard 11
Physics
