Answer:
Total time of moving at constant velocity = 50 seconds ( at C, E and G)
I think it is d if not then im sorry
<span>The initial speed, u of plane in terms of velocity of sound which may be taken as U
u=142/331=0.429*U
It crosses the sound barrier after says t seconds then we have 331-142=23.1*t or t is given 8.18 s exactly t=9/11s.
After 18 seconds the plane will traveling with velocity V
V=142+18*23.1=557.8 m/s==1.685*U</span>
Explanation and answer:
To solve this problem, we use the kinematics equation:
v^2-u^2=2aS .........................(1)
where
assuming the positive direction is downwards)
v = final velocity (when it reaches ground)
u = 0 = initial velocity (when it was dropped, or released, with zero vertical velocity).
a = 9.81 m/s^2 = acceleration due to gravity (on earth's surface)
S = 90m = distance travelled.
Substitute values into (1)
v^2 - 0^2 = 2*(9.81)*90
v^2 = 1765.8 m^2/s^2
v = sqrt(1765.8) m/s
= 42.02 m/s
= 42 m/s (to two significant figures).