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Standard XII

Physics

Acceleration

On a horizont...

Question

On a horizontal smooth surface a disc is placed at rest. Another disc of same mass is coming with impact parameter equal to its own radius. First disc is of radius r. What should be the radius of coming disc so that after collision first disc moves at an angle $45^{o}$ to the direction of motion of incoming disc?

2 r

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r (\sqrt{2} - 1)

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\frac{r}{(\sqrt{2} - 1)}

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r \sqrt{2}

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Solution

The correct option is B $\frac{r}{(\sqrt{2} - 1)}$
$b = (r + r_{2}) sin 45^{o}$
$r_{2} = (r + r_{2}) \frac{1}{\sqrt{2}}$
$\sqrt{2} r_{2} = r + r_{2}$
$(\sqrt{2} - 1) r_{2} = r$
$r_{2} = \frac{r}{\sqrt{2} - 1}$

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The correct option is B r(√2−1)b=(r+r2)sin45o r2=(r+r2)1√2 √2r2=r+r2 (√2−1)r2=r r2=r√2−1

The correct option is B $\frac{r}{(\sqrt{2} - 1)}$
$b = (r + r_{2}) sin 45^{o}$
$r_{2} = (r + r_{2}) \frac{1}{\sqrt{2}}$
$\sqrt{2} r_{2} = r + r_{2}$
$(\sqrt{2} - 1) r_{2} = r$
$r_{2} = \frac{r}{\sqrt{2} - 1}$