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the elevation at ground level is o feet. an elevator starts 90 feet below ground level.
after traveling for 15 seconds, the elevator is 20 feet below ground level. which
statement describes the elevator's rate of change in elevation during this 15-second
interval?
a
the elevator traveled upward at a rate of 6 feet per second.
the elevator traveled upward at a rate of 4 feet per second.
b
c
the elevator traveled downward at a rate of 6 feet per second.
d
the elevator traveled downward at a rate of 4 feet per second.

Step-by-step explanation:

If we graph elevation vs time, the rate of change is the slope of the line.

At t = 0, h = -90.

At t = 15, h = -20.

m = (-20 − (-90)) / (15 − 0)

m = 70/15

m = 4.67

The closest answer is B.  The elevator traveled upward at a rate of 4 feet per second.

, ; dcbsdkmnld

step-by-step explanation:

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.