The law of conservation of energy states that energy is not created nor destroyed, rather it is only transferred or transmitted from one form to another. Now, the work exerted which is the input is only transformed to move the object which is now becomes the output work. Some are used to move the object, some are converted to other forms. That is why it is never greater than the input energy. Thank you for your question. Please don't hesitate to ask in Brainly your queries.
One of the equations of gravity is this:

Where v = final velocity which is 7m/s
u = initial velocity which is 0 for objects falling from a height
g = acceleration due to gravity and it is approximately 10m/s^2. It's a constant so pretty much remember this number. It's positive since the work being done is caused by gravity (in other words, it's falling down). It can also be negative if the work being down is against gravity (in other words, it's going up)
h = height of object
Substitute for the values and you should have something like this



Answer:
The final velocity of the thrower is
and the final velocity of the catcher is
.
Explanation:
Given:
The mass of the thrower,
.
The mass of the catcher,
.
The mass of the ball,
.
Initial velocity of the thrower, 
Final velocity of the ball, 
Initial velocity of the catcher, 
Consider that the final velocity of the thrower is
. From the conservation of momentum,

Consider that the final velocity of the catcher is
. From the conservation of momentum,

Thus, the final velocity of thrower is
and that for the catcher is
.
Answer:
C
Explanation:
An element is a pure substance that can not be broken down into anything simpler
A compound in also a pure substance held together in fixed proportion through chemical bonds