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:
Explanation:
(a) The given figure is a convex lens.
(b) In this figure, the object is placed between F and optical center of a lens. Convex lens is a converging lens. It converges the beam of light falling on it after reflection. The image is formed on the same side of the lens as the object.
The formed image is enlarged and it is virtual and erect.
(i) Type : virtual
(ii) Orientation : upright
(iii) Size : Enlarged
Can you please give the phrases?
But, I'll help what I can.
First, he was the first to discover gravity. He was not bonked by the head by an apple, rather he watched an apple fall from a tree before he decided to explore gravity further.
He was also the first scientist to be knighted, which is a great honor, as you can expect.
Newton also developed The Three Laws of Motion. They are extremely important to physics and are considered some of the foundation for physics today.
He also discovered calculus, which is complex math that is very helpful to scientists today.
He also discovered the color spectrum using a glass prism, a dark room and window shade with a hole in it. He was able to project the color spectrum onto a piece of paper.
Those are the few I can think of now, but hope it helps!
The equivalent resistance of several devices connected in parallel is given by

where

are the resistances of the various devices. We can see that every time we add a new device in parallel, the term

increases, therefore the equivalent resistance of the circuit

decreases.
But Ohm's law:

tells us that if the equivalent resistance decreases, the total current in the circuit increases. The power dissipated through the circuit (and so, the heat produced) depends on the square of the current:

therefore if there are too many devices connected in parallel, this can be a problem because there could be too much power dissipated (and too much heat) through the circuit.