A trebuchet wasa hurling machine builtto attackthe walls of a castle under siege. A large stone could be hurled against a wall to break apart the wall. The machine was not placed near the wall because then arrows could reach itfrom the castle wall. Instead, itwas positioned so that the stone hit the wall during the second half of its flight. Suppose a stone is launched with a speed ofv0= 28.0 mls and at an angle ofθ0= 40.0°. What is the speed of the stoneif it hits the wall (a) just as it reaches the top of its parabolic path (b) when it has descended to half that height? (c) As a percentage, how much faster is it moving in part (b) than in part (a)?

Explanation:

Vo = 28m/s[40o].

Xo = 28*Cos40 = 21.45m/s.

Yo = 28*sin40 = 18 m/s.

a. Y = 0, V = Xo = 21.45 m/s.

b. Y^2 = Yo^2 + 2g*h = 0.

h = -Yo^2/2g = -(18^2)/-19.6 = 16.5m, max.

Y^2 = Yo^2 + 2g*h/2. = 0 + 19.6*8.35 =

163.66.

Y = 12.8 m/s.

V = Sqrt(Xo^2 + Y^2).

c. (Xo+Y) - Xo = (20.1+12.8i) - 20.1 =

12.8i = 12.8m/s[90o].

when you were answer but see its to late ;/

Explanation:

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

the best answer for these questions would be:

1.            c. is smaller

2.            d) concrete operational

3.            b) interaction with the environment – the children interact with their environment can them learn more.

4.            a) parents who reason openly with children can limit a child’s cognitive ability.