Answer:
Answer D : about 1067 meters
Explanation:
There are two steps to this problem:
1) First find the time it takes the plane to stop using the equation for the acceleration:
Where Vf is the final velocity of the plane (in our case: zero )
Vi is the initial velocity of the plane (in our case: 80 m/s)
is the acceleration (in our case -3 m/s^2 - notice negative value because the velocity is decreasing)
with units corresponding to seconds given the quantities involved in the calculation.
2) Second knowing the time it took the plane to stop, now use that time in the equation for the distance traveled under accelerated motion:
Where the answer results in units of meters given the quantities used in the calculation.
We round this to 1067 meters
5-14 m/s in 3 seconds
a=vf-vi/t
a=14-5/3
a=9/3
a=3 m/s^2
Energy to lift something =
(mass of the object) x (gravity) x (height of the lift).
BUT ...
This simple formula only works if you use the right units.
Mass . . . kilograms
Gravity . . . meters/second²
Height . . . meters
For this question . . .
Mass = 55 megagram = 5.5 x 10⁷ grams = 5.5 x 10⁴ kilograms
Gravity (on Earth) = 9.8 m/second²
Height = 500 cm = 5.0 meters
So we have ...
Energy = (5.5 x 10⁴ kilogram) x (9.8 m/s²) x (5 m)
= 2,696,925 joules .
That's quite a large amount of energy ... equivalent to
straining at the rate of 1 horsepower for almost exactly an
hour, or burning a 100 watt light bulb for about 7-1/2 hours.
The reason is the large mass that's being lifted.
On Earth, that much mass weighs about 61 tons.
Your answer would be true. Because if we didn't have those pieces of evidence, we wouldn't know about a lot of the ancient civilizations that we know today without that. Small pieces of evidence like that can help us to determine how they lived, or what they used to do, or even what they ate.
