Answer:
The recoil speed of the man and rifle is .
Explanation:
The expression for the force in terms of mg is as follows;
F=mg
Here, m is the mass and acceleration due to gravity.
Rearrange the expression for mass.
Calculate the combined mass of the man and rifle.
Put .
The expression for the conservation of momentum is as follows as;
Here, is the mass of the man and rifle, is the mass of the rifle, are the initial velocities of the man and bullet and are the final velocities of the man and rifle and rifle.
It is given in the problem that a rifle with a weight of 25 N fires a 4.5-g bullet with a speed of 240 m/s.
Convert mass of rifle from gram to kilogram.
Put , , , and .
Therefore, the recoil speed of the man and rifle is .
The reason wearing multiple thin layers will keep you warmer than a single thicker layer is because warm air is trapped between the layers acting as an insulator. If you were then to remove a layer you would reduce the amount of heat trapped which would cool you down.
Following the definition of the center of mass, "In physics, the center of mass of a distribution of mass in space is the unique point where the weighted relative position of the distributed mass sums to zero."
(see explanation below)