1 ) If the acceleration due to gravity at the earth’s
surface is ( 9.8m/s2 ) and the mass of the earth is 80
times that of the moon and radius of earth 4 times that moon, the value of g at
the moon’s surface will be ?
A
) 9.8m/s2 , B
) 1.96 m/s2 ,
C
) 4.9m/s2 , D
) None of these ,
Correct
Answer : - B ) 1.96
m/s2 ,
Solution
: -
Given
Data : -
·
ge =
9.8 m/s2 { ge = gravitational acceleration of
earth } ,
·
Me
= 80 * Mm { Me = mass of earth
, Mm = mass of moon } ,
·
Re = 4 * Rm { Re
= Radius of earth , Rm = Radius
of moon } ,
·
gm = ?
,
Formula
: -
ge = GMe / (Re)^2 ,
So ,
Ø ge = G(80*Mm) / (4*Rm)^2
Ø ge = (80)GMm / (16)(Rm)^2
Ø ge = (5)GMm / (Rm)^2 ,
Ø ge = 5
* gm ,
Ø 9.8 = 5 * gm
, (ge = 9.8 m/s2 )
Ø gm =
9.8 / 5 ( m / s2 ) ,
Ø gm = 1.96 m / s2 ,
Answer .
2
) Centre of gravity is a point , where
the whole ……………….. of body is to be centered .
A ) mass , B
) weight ,
C ) Both of these , D
) None of these ,
Correct
Answer : - B ) weight ,
3
) Find the velocity of pendulum in SHM
which has amplitude of 0.2 m and time period of 0.01 sec ?
A ) 20 π , B ) 30 π ,
C ) 40 π , D ) None of these ,
Correct
Answer ; - C ) 40 π ,
Solution
: -
Given
Data : -
·
T
= 0.01 s ,
·
Xo = 0.2 m
,
·
v
= ?
Formula
: -
v
= r w .
So first we have to find value of omega ( w ) , so
Ø w = 2 π / T
,
Ø w = 2 π / (0.01) ,
Ø w = 200 π .
So We simply
put it formula : -
Ø v = rw
,
Ø v = Xo * w
,
Ø v = (
0.2 ) * ( 200 π ) ,
Ø v = 40 π
. Answer
5
) Centre of mass is a point , where the
whole …………… of body is to be centered
.
A ) mass , B
) weight ,
C ) Both of these , D
) None of these ,
Correct
Answer : - A ) mass ,
Now go to online quiz section and check your preparation by this link : -
