Questions
From the top of a tower of height 40 m a ball is projected upwards with a speed of 20 m/sec at an angle of elevation of 30o. Then the ratio of the total time taken by the ball to hit the ground to its time of flight (time taken to come back to the same elevation) is (take g = 10 m/sec2)
detailed solution
Correct option is A
t=2usinθg=2×20sin3010=2sNow we shall calculate the total time taken by the ball to hit the ground. Using s=ut+12gt2, we have 40=−10t′+12×10×t′2∵ 4=−20sin30∘=−10m/s or 5t′2−10t′−40=0 or t′2−2t′−8=0 or t′=4s∴ t′t=4s2s=21Similar Questions
A ball is projected upwards from the top of a tower with a velocity of 50 ms-1 making an angle of 30° with the horizontal. The height of the tower is 70 m. After how many seconds from the instant of throwing will the ball reach the ground ?
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