As we know that gravitational potential energy is given by

here we have
m = mass = 120 kg

h = height = 8.2 m
now from above formula


so above is the gravitational potential energy of the couch
Operant conditioning, sometimes called <em>instrumental learning</em>, was first extensively studied by Edward L. Thorndike, who observed the behavior of cats trying to escape from home-made puzzle boxes.
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Answer:
They contain iron.
Explanation:
Iron is made of metal and magnets attract to metal Iron.
The acceleration due to gravity is given as:
g = GM/r²
<h3>
Derivation of gravitational acceleration:</h3>
According to Newton's second law of motion,
F = ma
where,
F = force
m = mass
a = acceleration
According to Newton's law of gravity,
F<em>g </em>= GMm/(r + h)²
F<em>g = </em>gravitational force
From Newton's second law of motion,
F<em>g </em>= ma
a = F<em>g</em>/m
We can refer to "a" as "g"
a = g = GMm/(m)(r + h)²
g = GM/(r + h)²
When the object is on or close to the surface, the value of g is constant and height has no considerable impact. Hence, it can be written as,
g = GM/r²
Learn more about gravitational acceleration here:
brainly.com/question/2142879
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Answer
given,
Side of copper plate, L = 55 cm
Electric field, E = 82 kN/C
a) Charge density,σ = ?
using expression of charge density
σ = E x ε₀
ε₀ is Permittivity of free space = 8.85 x 10⁻¹² C²/Nm²
now,
σ = 82 x 10³ x 8.85 x 10⁻¹²
σ = 725.7 x 10⁻⁹ C/m²
σ = 725.7 nC/m²
change density on the plates are 725.7 nC/m² and -725.7 nC/m²
b) Total change on each faces
Q = σ A
Q = 725.7 x 10⁻⁹ x 0.55²
Q = 219.52 nC
Hence, charges on the faces of the plate are 219.52 nC and -219.52 nC