Disk of mass slides on a smooth horizontal table towards identical disk which is at rest

PHYSICS · Single correct · CBSE · Physics · Work, Energy and Power · Work, Energy and Power

Problem

Disk

P

of mass

0.15\,\text{kg}

slides on a smooth horizontal table towards identical disk

Q

which is at rest. The speed of

P

just before collision is

2.0\,\text{m\,s}^{-1}

. After a perfectly elastic collision,

P

moves at

30^{\circ}

north of east. Which pair of values for the speed of

Q

and the angle it makes south of east immediately after the collision is correct? (a)

1.5\,\text{m\,s}^{-1},\;60^{\circ}

(b)

1.0\,\text{m\,s}^{-1},\;60^{\circ}

(c)

1.15\,\text{m\,s}^{-1},\;45^{\circ}

(d)

1.0\,\text{m\,s}^{-1},\;30^{\circ}