Solution :
The motion in the y direction.
The time taken by the toy rocket to hit the ground,

S = distance travelled = 30 m
u = 0 m/s
a = 
t= time in seconds
Therefore, 
t = 2.47 sec
Now motion in the x direction,
u = 12 m/sec

Upon integration 'v' with respect to 't'

Once again integrating with respect to t,


= 0.0176+29.64
= 29.65 m
Therefore, the toy rocket will hit the ground at 29.65 m from the building.
Answer:
v=9.6 km/s
Explanation:
Given that
The mass of the car = m
The mass of the truck = 4 m
The velocity of the truck ,u= 12 km/s
The final velocity when they stick = v
If there is no any external force on the system then the total linear momentum of the system will be conserve.
Pi = Pf
m x 0 + 4 m x 12 = (m + 4 m) x v
0 + 48 m = 5 m v
5 v = 48

v=9.6 km/s
Therefore the final velocity will be 9.6 km/s.
Answer C. 1.scientists learn by using the law of superposition B