Answer:
The initial velocity is 50 m/s.
(C) is correct option.
Explanation:
Given that,
Time = 10 sec
For first half,
We need to calculate the height
Using equation of motion

 ....(I)
....(I)
For second half,
We need to calculate the time
Using equation of motion



Put the value of h from equation (I)


According to question,


Put the value of t₁ and t₂



Here, g = 10 
The initial velocity is


Hence, The initial velocity is 50 m/s.
 
        
             
        
        
        
Answer:
length of the ladder is 13.47 feet
base of wall to latter distance 6.10 feet
angle between ladder and the wall is 26.95°
Explanation:
given data 
height h  = 12 feet 
angle 63°
to find out
length of the ladder ( L) and length of wall to ladder ( A) and angle between  ladder and the wall
solution
we consider here angle between base of wall and floor is right angle 
we apply here trigonometry rule that is 
sin63 = h/L
put here value 
L = 12 / sin63 
L = 13.47
so length of the ladder is 13.47 feet
and 
we can say 
tan 63 = h / A
put here value
A = 12 / tan63
A = 6.10
so base of wall to latter distance 6.10 feet
and 
we say here
tanθ = 6.10 / 12 
θ = 26.95°
so angle between ladder and the wall is 26.95°
 
        
             
        
        
        
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In this item, we let x be the rate of the boat in still water and y be the rate of the current.
Upstream. When the boat is going upstream, the speed in still water is deducted by the speed of the current because the boat goes against the water. The distance covered is calculated by multiplying the number of hours and the speed.
                 (x - y)(3) = 144
Downstream. The speed of the boat going downstream is equal to x + y because the boat goes with the current.
                (x + y)(2) = 144
The system of linear equations we can use to solve for x is,
                  3x - 3y  = 144
                  2x + 2y = 144
We use either elimination or substitution.
 
We solve for the y of the first equation in terms of x,
                   y =  -(144 - 3x)/3
Substitute this to the second equation,
            2x + 2(-1)(144 - 3x)/3 = 144
The value of x from the equation is 60
<em>ANSWER: 60 km/h</em>