Please Someone help me

The answer would be the last one.

Checks and balances is all 3 branches (legislative, executive and judicial) checking each other so no branch is abusing their power.

Example: The legislative branch is checked by the executive branch because the president can veto a law

vi = 3.95 m/s

Explanation:

We can apply the Work-Energy Theorem as follows:

W = ΔE = Ef - Ei

W = - Ff*d

then

Ef - Ei = - Ff*d  

If

Ei = Ki + Ui = 0.5*m*vi² + m*g*hi = 0.5*m*vi² + m*g*hi = m*(0.5*vi² + g*hi)

hi = d*Sin 20º = 5.1 m * Sin 20º = 1.7443 m

Ef = Kf + Uf = 0 + 0 = 0

As we know,   vf = 0  ⇒ Kf = 0

Uf = 0  since hf = 0

we get

W = ΔE = Ef - Ei = 0 - m*(0.5*vi² + g*hi)  ⇒   W = - m*(0.5*vi² + g*hi)   (I)

If

W = - Ff*d = - μ*N*d = - μ*(m*g*Cos 20º)*d = -  μ*m*g*Cos 20º*d    (II)

we can say that

- m*(0.5*vi² + g*hi) = -  μ*m*g*Cos 20º*d  

⇒ vi = √(2*g*(μ*Cos 20º*d - hi))  

⇒ vi = √(2*(9.81 m/s2)*(0.53*Cos 20º*5.1m - 1.7443 m)) = 3.95 m/s