Two vectors have a sum a and their difference is b. if a=b then, the angle between the two vectors is
a)0 b)45 c)120 d)90
(all the options are in degree)

D.90°

Explanation:

First remember that the magnitude of a vector , lets say T is the square of the dot product with itself.

This is to say

|T|=√(T×T)

Assume A≠0 and B≠0 then

Square both sides of the below equation

|A+B|²=|A-B|²

(A+B)²=(A-B)²

A(A+B)+B(A+B)=A(A-B)-B(A-B)

A²+AB+AB+B²=A²-AB-AB+B²

A²+2AB+B²=A²-2AB+B²

You notice that  it simplifies to

2AB= -2AB

This means that A×B =0

Hence the angle between the vectors should be 90°

most voltage drop calculators want the distance between the source and destination. then internally, they double it so both the source and return wires are calculated. but you need to know which distance the calculator uses so you're not half of what you should be or double what you should be.

most circuit breakers will not take a #6 directly, so the electrician will have to splice on a smaller pigtail. you also have to upsize the grounding wire when you upsized the ungrounded (hot) wire (see note in 250.122). this will preclude using most cable assemblies, as a cable with #6 copper will most likely only have a #10 grounding conductor. you need a #6 grounding conductor if the circuit is 20a. a #8 cable is no better, as it will have a #10 grounding conductor too. but most 20a breakers will take a #8 directly.

in your related post, you didn't say what type of load this is. if it is a light or heater, voltage drop won't be a big issue. if this is a motor, the current needs are huge at startup and the voltage drop can pose a problem. if this is a motor, knowing if the motor is under much load during startup will answer the voltage drop effect (a saw is easier to start than a compressor).

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.