Answer:
(d) a net external force must be acting on the system
Explanation:
Momentum is given as the product of mass and velocity.
P = MV
According to Newton's second law of motion, " Force applied to a body (system) is directly proportional to the rate of change of momentum of the body (system) which takes place in the direction of the applied force (external force).
F ∝ΔMV
Therefore, If the total momentum of a system is changing, a net external force must be acting on the system.
(d) a net external force must be acting on the system
Answer:
The atomic mass unit is 1/12 of an atom of carbon 12, and is a very small amount to represent in kilograms:

is atomic mass unit.
This is why the benefits of the atomic mass unit is that it makes the representation of atomic masses easier in terms of the simplicity of the numbers that are used to represent the masses. Also using the atomic mass unit it is easier to compare the masses of different atoms, These numbers would be very small and would require negative powers of 10 to represent them, so it is more convenient to use the atomic mass unit.
Straw polls are considered to be a form of biased sampling. An example of a straw poll is an unofficial vote like who you would like to be the President without actually casting your ballot.
That depends on how soon you want it to reach 5 m/s/s. Without friction, ANY force will accelerate the car, like a mosquito pushing on it, but a Space Shuttle booster will accelerate it at a greater rate.