The spring-mass system moves by simple harmonic motion, where there is a continuous conversion from elastic potential energy to kinetic energy and viceversa.
The total mechanical energy of the system at any moment of the motion is

where the first term U is the elastic potential energy, with k being the spring constant and x the displacement of the spring with respect to its rest position, and the second term K is the kinetic energy, with m being the mass of the object attached to the spring and v its speed.
The total energy E is constant during the oscillation of the spring, but the values of U and K change. In fact, when the displacement of the spring is maximum (x is maximum), then all the energy is potential energy U, because the speed of the object is zero (it's the moment when the mass is changing direction). On the contrary, when the mass crosses the equilibrium position (rest position) of the spring, then the potential energy is zero (U=0) because the displacement is zero (x=0), and so all the energy is kinetic energy of the motion, and so K is maximum.
2.1 kg of sodium bicarbonate is equal to the 2.1 x 10¹² ng of sample. Option D is correct.
Mass is the quantity of the substance in the body or object. The SI unit of mass is Kilogram.
There are other units of measure,
- Milligram: 1 g is equal to the

- Micro-gram: 1 g is equal to

- Nano-gram: 1 g is is equal to
First convert kg to gram,
Since, 1 Kg = 1000 g
2.1 kg = grams of sample
So,
Do the cross multiplication,

Now, convert 2100 g to nano-grams
Since, 1 g = 1 x 10⁹ ng
2100 g = ng of sample
So,
Do the cross multiplication,

Therefore, 2.1 kg of sodium bicarbonate is equal to the 2.1 x 10¹² ng of sample.
To know more about Mass units,
brainly.com/question/489186
Given the index of refraction, n and speed of light in the vacuum, c, we can solve for the speed of light in the transparent substance by the equation below.
n = c / v
where v is our unknown.
Substituting the known values,
1.7 = (3 x 10^8 m/s) / v
The value of v is equal to 1.76 x 10^8 m/s.
Answer:
a) 3.0×10⁸ m
b) 0 m
Explanation:
Displacement is the distance from the starting position to the final position.
a) In half a year, the Earth travels from one point on the circle to the point on the exact opposite side of the circle (from 0° to 180°). The distance between the points is the diameter of the circle.
x = 2r
x = 2 (1.5×10⁸ m)
x = 3.0×10⁸ m
b) In a full year, the Earth travels one full revolution, so it ends up back where it started. The displacement is therefore 0 m.
Answer: T2 = 7.07s
Explanation: The period of a loaded spring of spring constant k and mass m is given by
T= 2π √m/k
With 2π constant and k, it can be seen with little algebra that
T² is proportional to mass m
Hence (T1)²/m1 = (T2) ²/m2
Where T1 = 5, T2 =?, let m1 = m hence m2 = 2m.
By substituting, we have that
5²/m = (T2) ²/2m
25 / m = (T2) ²/2m
25 × 2m = (T2) ² × m
25 × 2 = (T2) ²
50 = (T2) ²
T2 = √50
T2 = 7.07s