Question #dcfec

2 Answers
SCooke · Sunayan S
Oct 2, 2017

#-0.85m# 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).
#PE_"grav" = m xx g xx h#

where
m = mass (kg)
g = 9.8 N/kg
h = height (m)
#900 = 80 xx 9.8 xx h# ; #h = 900/(80 xx 9.8) = 1.15m#

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

Sunayan S
Oct 2, 2017

See the answer below...

Explanation:

Suppose,it is at the initial height #color(red)h# meter.

Hence at the toppest point it has potential energy of #80xxgxx(h+2)#joule

As any point of a body moving in a vertical way has a constant mechanical energy so we can write that:-
#80xxgxx(h+2)=900#
#=>80xx10xx(h+2)=900#
#=>h+2=1.125#

Here something wrong...
Need the question to be double checked...as #color(red)h# becomes #-ve#
Though height might be negative but in this case...

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