Question

body falls on the surface of the earth from
a height of 20 cm. If after colliding with the
earth, its mechanical energy is lost by 75%, then
determine height upto the body would reach :-
) 5 cm (2) 10 cm (3) 20 cm (4) 15 cm​

Answer 1

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we know that

escape velocity is given as

v = [2GM/R]1/2

so, for earth

ve = [2GMe/Re]1/2

and

for planet

vp = [2GMp/Rp]1/2

now, we have the radii

Rp = 2Re

and as densities are same

ρp = ρe

or [as ρ = mass/volume]

Me/(4/3)πRe3 = Mp/(4/3)πRp3

so,

Me/Mp = Re3/Rp3 = Re3/(2Re)3 = 1/8

or

Mp = 8Me

now,

vp = [2GMp/Rp]1/2 = [2G.8Me/2Re]1/2

or

vp = 2.[2GMe/Re]1/2

so,

vp = 2ve

Answer 2

Answer:

15cm

hope it help

Explanation:

75/100*20

75/5

15