From the ground level a ball is to be shot with a certain speed. Graph shows the range R it will have versus the launch angle θ. The least speed the ball will have during its flight if θ is chosen such that the flight time is half of its maximum possible value, is equal to (Take g = 10 m/s²)

Question

G1 Physics · Accepted Answer

From the graph, the maximum range is 250 m. Thus u²/g = 250, and with g = 10 m/s², u = 50 m/s. The maximum possible time of flight is 2u/g = 10 s. Half of this is 5 s, so 2u sinθ/g = 5 gives sinθ = 1/2 and θ = 30°. The minimum speed during a flight occurs at the top and equals ucosθ = 50(√3/2) = 25√3 m/s. Hence option D.