Question

from the top of a tower of height 40m a ball is projected upward with a speedof 20m/sec at an elevation of 30degrees . 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 point of projection is g=10m/s

Answer 1

Time taken to reach maximum height in a horizontal projection :

H = 20²sin²30° / 2 × 10

H = (400 × 0.25) / 20 = 5m

Total height is :

5 + 40 = 45 m

Time of flight = (2 × 20 × Sin 30) / 10 = 2 seconds

Time of free fall is √(2 × 45)/10 = √9 = 3 seconds.

The total time taken to reach the ground is thus :

1 + 3 = 4 Seconds

The ratio is thus :

4 : 2

Answer 2

Answer:

Explanation:

s=−40m,u=+10ms−1,a=−10ms−2

Now s=ut+12at2

=> −40−10t+12×(−10)t2

=> r2−2t−8=0

=> (t+2)(t−4)=0

=> t=−2or4s

The negative value of t is not possible

Hence the ball will hit the ground after 4 s

and find the time of flight by T=2USINTHETA/G

Hope it helps!