The work done to pull the sister back on the swing is equal to the increase in potential energy of the sister:

(1)
where m is the sister's mass, g is the gravitational acceleration and

is the increase in altitude of the sister with respect to its initial position.
By calling

the angle of the chain with respect to the vertical, the increase in altitude is given by

(2)
where L is the length of the chain.
Putting (2) inside (1), we find

from which we can find the mass of the sister:
Answer:
plants depend on animals for CO2 (to use during photosynthesis) while animals depend on plants for food (consumation)
Explanation:
Answer:
Action - Pulling up the train.
Reaction - Friction on the locomotive
Explanation:
Locomotive is pulling the train upwards ,
Which is the action force applied by the locomotive,
As a reaction locomotive will be pulled by the train which is the reaction of pulling
Now, considering it as a action on locomotive , friction force will act on it as a reaction upwards which will result to move it upwards.
For train action is pulling up by locomotive and reaction will be friction acting on it downwards.