# Question #dcfec

Oct 2, 2017

$- 0.85 m$ It is underground!

#### Explanation:

At the "initial" location, the object's energy is all "potential". The rate of fall is not a part of the question - only the distance from the start (-2m).
$P {E}_{\text{grav}} = m \times g \times h$

where
m = mass (kg)
g = 9.8 N/kg
h = height (m)
$900 = 80 \times 9.8 \times h$ ; $h = \frac{900}{80 \times 9.8} = 1.15 m$

$1.15 - 2 = - 0.85 m$ It is underground!

Oct 2, 2017

#### Explanation:

Suppose,it is at the initial height $\textcolor{red}{h}$ meter.

Hence at the toppest point it has potential energy of $80 \times g \times \left(h + 2\right)$joule

As any point of a body moving in a vertical way has a constant mechanical energy so we can write that:-
$80 \times g \times \left(h + 2\right) = 900$
$\implies 80 \times 10 \times \left(h + 2\right) = 900$
$\implies h + 2 = 1.125$

Here something wrong...
Need the question to be double checked...as $\textcolor{red}{h}$ becomes $- v e$
Though height might be negative but in this case...