Answer: Base units
The principal SI units that are used to derive all other SI units are called base units. The base units are the units of fundamental quantities e.g. M L T that is Mass, Length, and Time. All other physical quantities can be written in the fundamental dimension forms. The physical quantities are not measured directly but are build up from the building blocks that are the fundamental quantities which have base units.
A theory is a system of ideas that isn't exactly proven to be true fully. A law is a description of whatever scientific phenomena you're studying. All you need to know is a law describes, and a theory explains.
12 V is the f.e.m.

of the battery. The potential difference that is applied to the motor is actually the fem minus the voltage drop on the internal resistance r:

this is equal to the voltage drop on the resistance of the motor R:

so we can write:

and using

and

we can find the current I:
Answer:
Its acceleration is positive
Explanation:
As the car is moving in the negative x-direction than after applying brake then there will be a decrease in the acceleration but in the opposite direction.
As decreasing acceleration consider to be negative but the car is moving in negative direction which means increasing acceleration is negative by sign convention but by applying brake acceleration decrease but in opposite direction than it will give positive value of acceleration.