No force is necessary to keep a moving object moving (in a straight line at a constant speed).
1. its must be B and 2. must be C
Answer:
n = 4 x 10¹⁸ photons
Explanation:
First, we will calculate the energy of one photon in the radiation:

where,
E = Energy of one photon = ?
h = Plank's Constant = 6.625 x 10⁻³⁴ J.s
c = speed of light = 3 x 10⁸ m/s
λ = wavelength of radiation = 567 nm = 5.67 x 10⁻⁷ m
Therefore,

E = 3.505 x 10⁻¹⁹ J
Now, the number of photons to make up the total energy can be calculated as follows:

<u>n = 4 x 10¹⁸ photons</u>
<span>A physical change is any change that alters the form or appearance of a substance but does not change it into another substance
-Some of the physical properties may be altered, but the chemical composition stays the same
-Examples: Bending, Crushing, Cutting, Melting, Freezing, Boiling</span>