Question

A ball is thrown upward at an angle of `45^(@)` with the horizontal and lands on the top edge of a builing that is 20 m away. The top edge is 10 m above the throwing point. The initial speed of the ball in metre/second is (take `g =10 m//s^(2)`)
A. 10 m/s
B. 20 m/s
C. 25 m/s
D. 30 m/s

Answer 1

Correct Answer - B

`y = x tan theta - (gx^(2))/(2u^(2) cos^(2) theta)`
`10 = 20 tan 45^(@) - (10 xx 400)/(2u^(2) xx cos^(2) 45^(@))`
`rArr u ~= 20 m//s`.