Erosion, weathering, mechanical changes, chemical changes.
Really, any interaction can change the composition of a rock whether it be done by man or through nature.
Answer:
50.4÷1.18= 42.7m/s as speed is equal to the distance over the time taken
Answer:
The crate's coefficient of kinetic friction on the floor is 0.23.
Explanation:
Given that,
Mass of the crate, m = 300 kg
One worker pushes forward on the crate with a force of 390 N while the other pulls in the same direction with a force of 320 N using a rope connected to the crate.
The crate slides with a constant speed. It means that the net force acting on it is 0. Net force acting on it is given by :

So, the crate's coefficient of kinetic friction on the floor is 0.23.
The classical physics works on the Newton's laws of motion. It is applicable on heavenly bodies which are governed by the gravitational force. On the other hand, Quantum Physics is applicable for very low mass and sized bodies like electron, protons etc. The classical physics would accurately describe the motion of satellite moving with speed 7500 m/s using the following formula:

where G is the gravitational constant, M is the mass of the planet and v is the orbital speed. Then radius of the orbit can be described by this formula.
The formular for determinatio of mass number is this:
Mass number = number of proton + number of neutron
From the question, we are told that:
Mass number = 39
Proton number = 19
Number of proton = ?
Number of neutron = mass number - number of proton
Number of neutron= 39 - 19 = 20
Therefore, number of neurtron = 20.