(ab/bc, non-calculator) the position function 2 st t ( ) 4.9 396.9   , gives the height (in meters) of an object that has fallen from a height of 396.9 meters after t seconds. (a) explain why there must exist a time t , 1 2  t  , at which the height of the object must be 382 meters above the ground. (b) find the time at which the object hits the ground. (c) find the average rate of change in s over the intervalt 8,9. include units of measure. explain why this is a good estimate of the velocity at which the object hits the ground. how can this estimate be improved? (d) evaluate: 3 ( ) (3) limt 3 st s  t   . show the work that leads to your answer. include units.

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).

grav potential energy

which piece of furniture will have the most inertia and give the furniture movers the most difficulty in moving?  

answer

a 75kg dining table

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2