As we know that friction force on box is given by

here we know that

here we have
m = 12 kg

so now we have

now we will have


so it required minimum 49 N(approx) force to move the block
Answer:
Explanation:
Given
1 ) 140 m west in 45 s .
2 ) 90 m east in 25 s .
a )
distance travelled in first 45 s = 140 m
b ) distance travelled in next 25 s = 90 m
c ) Total distance travelled = 140 m + 90 m
= 230 m
d ) average speed in first 45 s
= distance in 45 s 45
= 140 / 45 = 3.11 m /s
e ) average speed in next 25 s
distance in 25 s / 25
= 90 / 25 = 3.6 m /s
f ) average in entire trip
= total distance / total time
= (140 + 90) / ( 25 + 45 )
= 3.28 m /s
g )
displacement in first 45 s = 140 m towards west
h )
displacement in next 25 s = 90 m towards east
i )
total displacement = 140 - 90
= 50 m towards west .
The emissivity of the earth is 0.5
The emissivity of the earth is calculated by the Stefan's law

Answer:
A closest
Explanation:
This is because the electric field will be strongest or largestwhen the equipotential curves are closest together
We know that the field is
E= V/d
Where is distance and we see that d being the denominator will only make E bigger if it becomes smaller that is the curves closest