Answer:
The answer to your question is Ke = 2240 J
Explanation:
Data
mass of the object = 20 kg
mass of the girl = 50 kg
speed = 8 m/s
Kinetic energy = Ke = ?
Formula
Ke = 1/2 mv²
Process
Kinetic energy is due to the movement of an object.
1.- Calculate the total mass
Total mass = 20 + 50 = 70 kg
2.- Substitution
Ke = 1/2(70)(8)²
3.- Simplification
Ke = 1/2(4480)
4.- Result
Ke = 2240 J
Answer:

Explanation:
The first step is:

Second step is:

Multiplying second step by 2, and adding both the steps, we get that:

Cancelling common species, we get that:

Reaction of dissociation: Ag₂SO₄ → 2Ag⁺ + SO₄²⁻.
m(Ag₂SO₄) = 4 g.
V(Ag₂SO₄) = 1 l.
n(Ag₂SO₄) = m(Ag₂SO₄) ÷ M(Ag₂SO₄).
n(Ag₂SO₄) = 4 g ÷ 311,8 g/mol.
n(Ag₂SO₄) = 0,0128 mol.
n(Ag⁺) = 2 · 0,0128 mol = 0,0256 mol.
n(Ag₂SO₄) = n(SO₄²⁻) = 0,0128 mol.
c(Ag⁺) = n ÷ V = 0,0256 mol ÷ 1 l = 0,0256 mol/l.
Ksp = c(Ag⁺)² · c(SO₄²⁻).
Ksp = (0,0256 mol/l)² · 0,0128 mol/l.
Ksp = 8,3·10⁻⁶.
The percent yield of the reaction : 89.14%
<h3>Further explanation</h3>
Reaction of Ammonia and Oxygen in a lab :
<em>4 NH₃ (g) + 5 O₂ (g) ⇒ 4 NO(g)+ 6 H₂O(g)</em>
mass NH₃ = 80 g
mol NH₃ (MW=17 g/mol):

mass O₂ = 120 g
mol O₂(MW=32 g/mol) :

Mol ratio of reactants(to find limiting reatants) :

mol of H₂O based on O₂ as limiting reactants :
mol H₂O :

mass H₂O :
4.5 x 18 g/mol = 81 g
The percent yield :

I believe the correct answer is C. <span>Zn + CuCl2 —> ZnCl2 + Cu</span>