Two balls A and B are projected simultaneously from the top of a long smooth inclined plane. The ball A is projected along the surface with speed u while ball B is thrown horizontally with velocity v = 10 m/s, from the same point. Both the balls travel in the same vertical plane and the ball B hits the ball A on the incline. If the inclination angle of the incline is θ=cos−145, find the displacement (in meter) from the point of projection, where the two balls collide. Take g=10ms-2
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answer is 18.75.
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Detailed Solution
Let us fix our co-ordinate axes along the incline (x) and perpendicular to it (y),the acceleration of both the balls in x-direction is same equal to ax=gsinθ. ∴ The two balls will collide if the x-component of their initial velocities is equal. ⇒u=vcosθ∴u=10×45=8m/sThe time of flight of the projectile can be calculated by consideration of its motion in y-direction.0=(vsinθ)t−12(gcosθ)t2⇒t=2vsinθgcosθ=2×10×310×4=32sec∴ Distance PQ=ut+12(gsinθ)t2 =8×32+12×10×35×322=18.75m