What is fundamental quantity?​

Explanation:

Fundamental quantities are mass, time, current, length, temperature, amount of substance and luminous intensity. All other physical quantities are derived quantities and can be made from fundamental quantities. Momentum is the product of mass and velocity.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

find the sum of the two horizontal vectors and the sum of the two vertical vectors

isoceles right angled triangle