Question

If a stone is projected obliquely, then it follows
parabolic path under gravity. If height-time graph is
given as shown in figure, then the value of h in figure
is (g = 10 m/s2)
Height (m)
Tob
* Time (s)
1
2
50
(1) 20 m
(3) 25 m
(2) 10 m
(4) 40 m​

Answer 1

answer : option (1) 20m

explanation : let initial speed of particle is u inclined at an angle θ.

Time of flight, T = 2usinθ/g

from figure, T = 7sec

so, 7 = 2usinθ/10

⇒35 = usinθ.........(1)

now, using formula s = ut + 1/2 at²

here, s = OB, u = y component of initial velocity i.e., usinθ, a = -g = -10 and t = 2s

so, OB = usinθ(2) - 1/2 × 10 × (2)²

from equation (1),

OB = 35(2) - 5(2)² = 70 - 20 = 50 m

similarly, s = OA, a = -g = -10 , t = 1s , u = usinθ

so, OA = usinθ (1) - 1/2 × 10 × (1)²

= 35 - 5 = 30m

then, h = OB - OA = 50m - 30m = 20m

hence, option (1) is correct choice.

Answer 2

$\huge\bold\purple{Answer:-}$

(1) 20 m