Elston attaches a spring scale to a box and pulls it across the floor. He then places a book in the box and pulls it in the same distance with the same effort. How does the force change after the book is placed in the box?
Responses
it could increase or decrease depending on the weight of the book
it could increase or decrease depending on the weight of the book
it will increase
it will increase
it could increase or decrease depending on the weight of the box
it could increase or decrease depending on the weight of the box
it will decrease
it will decrease
The force measured by the spring scale will increase after the book is placed in the box, assuming all other factors remain the same (such as the coefficient of friction between the box and the floor, and the even distribution of effort). This is because the weight of the box has increased due to the added mass of the book, which in turn increases the normal force and likely the frictional force that needs to be overcome to pull the box across the floor.
So the correct response is:
it will increase