4 for sure because you dont want anything spilling on you or others that is harmful.
Answer:
The law of inertia
Explanation:
A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force
Answer:
The observed wavelength on Earth from that hydrogen atom is
.
Explanation:
Given that,
The actual wavelength of the hydrogen atom, 
A hydrogen atom in a galaxy moving with a speed of, 
We need to find the observed wavelength on Earth from that hydrogen atom. The speed of galaxy is given by :

is the observed wavelength

So, the observed wavelength on Earth from that hydrogen atom is
. Hence, this is the required solution.
Answer:
Density of 127 I = 
Also, 
Explanation:
Given, the radius of a nucleus is given as
.
where,
- A is the mass number of the nucleus.
The density of the nucleus is defined as the mass of the nucleus M per unit volume V.

For the nucleus 127 I,
Mass, M = 
Mass number, A = 127.
Therefore, the density of the 127 I nucleus is given by

On comparing with the density of the solid iodine,

Answer:
Explanation:
Given
Volume of paint is 
Area of cover 
Suppose paint to be a rectangular box with thickness t and volume V
therefore we can write as



