Answer:
v=2.42m/s
Explanation:
We use the energy conservation theorem in order to solve the problem. The energy when the spring is compressed is equal at the energy when the disk leaves the spring:

At the beginning the initial energy is totally potential, energy linked to the compressed spring. At the end the energy is totally kinetics
We solve the equation in order to find the speed.
k=162 N/m
x=7 cm=0.07m
m=0.135 kg

The answer is A.
A positive charge’s electric field pushes out.
Hope this helps! -Avenging
Answer:
13.5 J
Explanation:
mass of ball, m = 3 kg
maximum height, h = 2.8 m
initial speed, u = 8 m/ s
Angle of projection, θ
use the formula of maximum height


Sin θ = 0.926
θ = 67.8°
The velocity at maximum height is u Cosθ = 8 Cos 67.8 = 3 m/s
So, kinetic energy at maximum height

K = 0.5 x 3 x 3 x 3
K = 13.5 J
The visible wavelengths constructively reflected by the film when it is surrounded by air on both sides can be calculated using the equation:
lambda = 2t*(n2/n1)
where:
lambda is the wavelength,
t is the thickness, and;
n1 and n2 are indexes of refraction