Answer: 
Explanation:
Given
Mass of child 
speed of child is 
Moment of inertia of merry go round is 
radius 
Conserving the angular momentum

Answer:
(C)
Explanation:
Because the photons being different makes them have different amounts of energy, they both with have a precise and different energy from each other.
Answer:
The electric field is
and the ditection is from outer to inner side of the membrane.
Explanation:
We know the electric field (
) is given by
, 'V' being the potential.
In 1-D, it can be written as

where 'd' is the separation of space in between the potential difference is created.
Given,
and the thickness of the cell membrane is
.
Therefore the created electric field through the cell membrane is

Hello this is to other people looking for the answer. Everyone else is wrong. I just took the quiz on e2020. The answer actually Comparative. Your welcome. Have a nice day.
AS
work done =W = F.d = F d cosФ (Ф is angle between force F and displacement d) If a body/object is moving on a smooth surface (friction-less surface ) .There is no force acting on that body. F=0 so W=FdcosФ= (0)dcosФ ⇒ W=0
Now if a body is facing some amount of force but under the action of force there is no displacement covered. d=0 so W =FdcosФ= F(0)cosФ ⇒W=0
example: A person is applying a force on rigid wall but wall remains at rest there is no displacement occurs in wall.
The third term upon which work done dependent is angle between force and displacement i.e Ф. If Ф=90° then W= FdcosФ= Fdcos90⇒ W=0 ( as cos 90°=0)