Answer:
ΔU = 2 mg h
Explanation:
In a spring mass system the potential energy is U = m g h
where h is measured from the equilibrium point of the spring
the potential energy at the highest point is
U₁ = m g h
the potential energy at the lowest point is
U₂ = m g (-h)
instead in this energy it is
ΔU = 2 mg h
In this two points the kinetic energy is zero, but there is elastic potential energy that has the same value in the two points, so its change is zero
4.3A.
The easiest way to solve this problem is find the equivalent resistance for parallel resistor 1/Req = 1/R1 + 1/R2 + 1/R3 in the three-branch parallel network with branches whose resistance are 8Ω.
1/Req = 1/8 Ω + 1/8 Ω + 1/8 Ω
1/Req = 3/8 Ω
Req = 8/3 Ω = 2.667Ω
Req = 2.7Ω
So, the equivalent circuit will be the 20.0V battery in series with a resistor 2.0Ω and the equivalent resistor 2.7Ω.
Using Ohm's Law to find the current provide by the 20.0V voltage source:
V = I*R ------> I = V/R
I = 20.0V/(2.0Ω + 2.7Ω)
I = 20.0V/4.7Ω
I = 4.3A
