Salmon often jump waterfalls to reach their
breeding grounds.
starting downstream, 2.02 m away from a
waterfall 0.574 m in height, at what minimum
speed must a salmon jumping at an angle of
32 ◦
leave the water to continue upstream?
the acceleration due to gravity is 9.81 m/s
2
.
answer in units of m/s.

6.35 m/s

Explanation:

The motion of the salmon is equivalent to that of a projectile, which consists of two independent motions:

- A horizontal motion with constant speed

- A vertical motion with constant acceleration (, acceleration of gravity)

The horizontal velocity of the salmon is given by:

where

u = ? is the initial speed

is the angle of projection

Then the horizontal distance covered by the salmon after a time t is given by

Or equivalently, the time taken to cover a distance d is

(1)

Along the vertical direction, the equation of motion is

(2)

where

is the initial vertical velocity

If we substitute (1) into (2), we get:

We now that in order to reach the breeding grounds, the salmon must travel a distance of

d = 2.02 m

reaching a height of

h = 0.574 m

Substituting these data into the equation and solving for u, we find the initial speed that the salmon must have:

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).

mistakes are ok