Question

You pick up a 10-newton book off the floor and put it on a shelf 2 meters high. How much work did you do?​

Answer 1

Answer:

20 J of work is done by you, against gravity

Explanation:

Work done by gravity = Potential energy stored in the book after it is put ona shelf.

Potential energy stored:

$U = mgh$

$U = wh$

w= weight in Newton

m= mass of the book

g= acceleration due to gravity

h= height through which, it is raised.

Work is being done against gravity.

$U = 10 \times 2$

$U = 20 J$

Answer 2

Answer:

20 J

Explanation:

Given:

Weight of the book is, $W=10\ N$

Height or displacement of the book is, $d=2\ m$

The work done on the book to raise it to a height of 2 m on a shelf is against gravity. The gravitational force acting on the book is equal to its weight. Now, in order to raise it, an equal amount of force must be applied in the opposite direction.

So, the force applied by me should be equal to weight of the body and in the upward direction. The displacement is also in the upward direction.

Now, work done by the applied force is equal to the product of force applied and displacement of book in the direction of the applied force.

Therefore, work done is given as:

$Work=W\times d\\Work=10\times 2=20\ J$

Therefore, the work done to raise a book to a height 2 m from the floor is 20 J.