1 ) How much water a pump of 2kW can raise in one minute to a height of 10 m ?
A ) 120 kg , B ) 1200 kg
,
C ) 2400 kg , D ) None of
these ,
Correct
Answer : - B ) 1200 kg ,
Solution
: -
Given
data : -
P = 2 kW = 2000 W ,
t = 1 minute = 60 seconds ,
h = 10 m ,
Formula
: -
Here we have to find the mass ,
so first we will work : -
P = w / t ,
w = P x t = 2000 x 60 = 120000 J .
So now we can find mass : -
w = f . d ,
w = (mg) . d ,
120000 = (m x 10 ) . 10 ,
m =
1200 kg , Answer .
2 )
How do I calculate the electric power required to lift 100 kg of material of
height 5 m and 2 mins ?
A ) 34 W , B
) 41 W ,
C ) 53 W , D
) None of these ,
Correct
Answer : - B ) 41 W ,
Solution
: -
Given
data : -
m = 100 kg ,
t = 2 mins = 120 secs ,
d = 5 m ,
g = 9.81 m / s² ,
P = ?
Formula
: -
first we find force : -
F = mg = 100 x 9.81 = 981 N .
Now we find work : -
w = f . d ,
w = 981 x 5 = 4905 Nm or J .
Now we can power : -
P =
w / t = 4905 / 120 = 41 W , Answer .
3 )
Sum of magnitude of two forces acting at a point is 16 N . If the resultant
force is 8 N and its direction is perpendicular to smaller force , then forces will be : -
A ) 6 N , 12 N . B
)
C ) 8 N , 8 N . D ) None of these ,
Correct
Answer : -
Solution
: -
4 )
The maximum kinetic energy (K.E) of emitted photoelectrons depends on : -
A ) frequency of material , B ) nature of material ,
C ) independent of intensity of light , D ) All of these ,
Correct
Answer : - D ) All of these ,
