Answer:
162.78 m/s is the most probable speed of a helium atom.
Explanation:
The most probable speed:

= Boltzmann’s constant =
T = temperature of the gas
m = mass of the gas particle.
Given, m = 
T = 6.4 K
Substituting all the given values :


162.78 m/s is the most probable speed of a helium atom.
Answer:
Kinetic energy of an object can't be greater than potential energy.
Explanation:
This is due to the reason that some of the energy is lost in the form of friction, heat energy, light energy etc. For example, a ball bounces to a height h in its first bounce.
Johannes Kepler- he did it by observing the ‘Tycho Brahe’. His 3rd law was published 10 years later to his first two laws.
Answer:
The velocity of the acorn just before it reaches the ground is 19 m/s
The kinetic energy when hitting the ground is 3.1 J
Explanation:
Given;
mass of the acorn, m = 0.017 kg
height of fall, h = 18.5 m
Apply the law of conservation of mechanical energy;
mgh = ¹/₂mv²
gh = ¹/₂v²
v² = 2gh
v = √2gh
v = √(2 x 9.8 x 18.5)
v = 19 m/s
Thus, the velocity of the acorn just before it reaches the ground is 19 m/s
Now, determine the kinetic energy when hitting the ground;
K.E = ¹/₂mv²
K.E = ¹/₂(0.017)(19)²
K.E = 3.09 J
K.E = 3.1 J
Therefore, the kinetic energy when hitting the ground is 3.1 J