Question

I NEED HELP WITH THESE

I am pretty sure of my answers, so I just need someone to double check. Explanation is not needed because I know how to solve it, just needs to be checked. You can put one it you want.

Answer 1

1. (b) 500 km
2. (b) 6 seconds

Explanation:

1.

The semi-major axis length is √47196900 = 6870 km. That distance from the center of the Earth means the satellite is ...

6780 -6370 = 500 . . . km

from the surface of the Earth.

The satellite is a maximum of 500 km from the Earth.

(It is a minimum of 250 km from Earth.)

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2.

The equation has a zero at t=6. When the car's velocity is zero, it is at a complete stop.

The car comes to a complete stop when time is 6 seconds.

(The car is still being accelerated, so it doesn't stay stopped.)

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I prefer a graphing calculator for a quick solution. You can also solve this equation algebraically.

0 = 0.5t^2 -10.5t +45 . . . . t when v(t) = 0

t^2 -21t +90 = 0 . . . . . . . multiply by 2

(t -6)(t -15) = 0 . . . . . . . . factor

t = 6 or t = 15 . . . . . . . only t=6 is in the domain of the function