Afriend slides a box along a flat floor to you, which you slow by applying a force at a 30° angle. is the work you do to slow the box positive or negative? if you instead placed a book directly on top of the box as it passed you, what can you say about the work done by the book? a) positive, positive work doneb) positive, negative work donec) negative work, positive work doned) negative work, no work done

D) Negative work, No work done

Explanation:

As we know that work done is given as

here we know that

F = force

d = displacement

when the force and displacement are at acute angle with each other then the work done is positive and due to this the mechanical energy will increase

While in other case when the force and displacement are in opposite direction or at obtuse angle with each other then the work done is negative and it will decrease the mechanical energy

Now if the force and displacement are at perpendicular direction then the work done must be ZERO

so here we know that when we push against the motion to slow it down then the work done is negative while in other case when book is placed on it then force is perpendicular to the displacement so the work done is ZERO