Answer:
The correct answer is A
Explanation:
The question requires as well the attached image, so please see that below.
Coulomb's Law.
The electrical force can be understood by remembering Coulomb's Law, that describes the electrostatic force between two charged particles. If the particles have charges
and
, are separated by a distance r and are at rest relative to each other, then its electrostatic force magnitude on particle 1 due particle 2 is given by:

Thus if we decrease the distance by half we have

So we get

Replacing we get

We can then multiply both numerator and denominator by 4 to get

So we have

Thus if we decrease the distance by half we get four times the force.
Then we can replace the second condition

So we get

which give us

Thus doubling one of the charges doubles the force.
So the answer is A.
Answer:
Explanation:
60000 kJ / h = 60000 x 1000 / (60 x 60 )
= 16667 J /s
a)

where
and
are heat supplied and heat given from outside source .
Here
= 16667 J/s

= 15.684

16667 / W = 15.684
W= minimum power supplied = 1062.7 W.
b )
If 

=19.87



= 838.8 W .
Answer:
F = 51.3°
Explanation:
The component of weight parallel to the inclined plane must be responsible for the rolling back motion of the car. Hence, the force required to be applied by the child must also be equal to that component of weight:

where,
W = Weight of Wagon = 150 N
θ = Angle of Inclinition = 20°
Therefore,

<u>F = 51.3°</u>
Answer:
298,220 N
Explanation:
Let the force on car three is T_23-T_34
Since net force= ma
from newton's second law we have
T_23-T_34 = ma
therefore,
T_23-T_34 = 37000×0.62
T_23= 22940+T_34
now, we need to calculate
T_34
Notice that T_34 is accelerating all 12 cars behind 3rd car by at a rate of 0.62 m/s^2
F= ma
So, F= 12×37000×0.62= 22940×12= 275280 N
T_23 =22940+T_34= 22940+ 275280= 298,220 N
therefore, the tension in the coupling between the second and third cars
= 298,220 N