Answer:
You are exactly right. The molecules in hot air are moving faster than the molecules in cold air. Because of this, the molecules in hot air tend to be further apart on average, giving hot air a lower density. That means, for the same volume of air, hot air has fewer molecules and so it weighs less
Answer:

Explanation:
If m is the mass of the object and v is the velocity of the object. The kinetic energy is due to the motion of an object. It is given by the relation as follows :

The above formula is used to find the kinetic energy of an object.
The kinetic energy of the bullet is 20.4 kJ.
<u>Explanation:</u>
Kinetic energy of a bullet will be equal to the product of mass of the bullet with the square of velocity or speed of the bullet and then the half of that product value.
But here the mass of the bullet is not given, instead the weight of the bullet is given in terms of force. So from this, we have to first find the mass of the bullet.
We know that as per Newton's second law of motion, force is directly proportional to the product of mass and acceleration. So here the acceleration will be equal to the acceleration due to gravity as it is weight of the object.
So F = mg
0.10 N = m × 9.8
So ,the mass of the bullet is 0.0102 kg.
Now, we know the mass and velocity of the bullet is given as 2000 m/s.
So,
kinetic energy =
× m × v²
kinetic energy = 0.5 × 0.0102 × 2000 × 2000 = 20.4 kJ
Thus, the kinetic energy of the bullet is 20.4 kJ.
Answer:
B
Explanation:this is not physics