1.

The slopes of wind screen of two cars are `alpha_1=30^@ and alpha_2= 15^@` respectively. At what ratio `v_1/ v_2` of the velocities of the cars will their drivers see the hail stones bounced back by the wind screen on their cars in vertical direction? Assume hail stones fall vertically downwards and collisions to be elastic.

Answer» Correct Answer - C
`v_("absolute")` in vertically downward `v_(Hc)` after collision vertically upwards since collision is elastic so velocity of tailstones w.r.t car before and after collision will make equal angles.
`vecv_(Hc//1)=vecv_(H)-v_(c)=vecv-vecv_(1),beta+90-2beta+alpha_(1)=90`
`a_(1)=beta.2beta=2alpha_(1)tan 2beta=tan 2alpha_(1)=v_(1)/(v)`


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