1) 29.4 N
The force of gravity between two objects is given by:

where
G is the gravitational constant
M and m are the masses of the two objects
r is the separation between the centres of mass of the two objects
In this problem, we have
(mass of the Earth)
(mass of the box)
(Earth's radius, which is also the distance between the centres of mass of the two objects, since the box is located at Earth's surface)
Substituting into the equation, we find F:

2) 
Let's now calculate the ratio F/m. We have:
F = 29.4 N
m = 3.0 kg
Subsituting, we find

This is called acceleration of gravity, and it is the acceleration at which every object falls near the Earth's surface. It is indicated with the symbol
.
We can prove that this is the acceleration of the object: in fact, according to Newton's second law,

where a is the acceleration of the object. Re-arranging,

which is exactly equal to the quantity we have calculated above.
To solve this problem we will apply the concepts related to wavelength, as well as Rayleigh's Criterion or Optical resolution, the optical limit due to diffraction can be calculated empirically from the following relationship,

Here,
= Wavelength
d= Diameter of aperture
= Angular resolution or diffraction angle
Our values are given as,

The frequency of the sound is 
The speed of the sound is 
The wavelength of the sound is

Here,
v = Velocity of the wave
f = Frequency
Replacing,


The diffraction condition is then,

Replacing,

d = 0.24 m
Therefore the diameter should be 0.24m
Answer:
F_B = 6.4*10^-13 N
Explanation:
The magnetic force on the electron, generated by the motion of the electron and the magnetic field is given by:

q: electron charge = 1.6*10^{-19}C
v: speed of the electron = 2.0*10^6 m/s
B: magnitude of the magnetic field = 2T
However, the direction of B and v are perpendicular between them. So, the angle between vectors is 90°. The magnitude of the magnetic force is:

You replace the values of q, v and B in the last equation:

hence, the magnetic force on the electron is 6.4*10^-23 N
CHARLES'S LAW
At a constant pressure, the volume of a given amount of gas is directly proportional to its absolute temperature.