# Find the force to push a book sideways on a table

## Homework Statement

Place a book flat on a table and press down on it with your hand. Now suppose the hand-book and table- book values of are 0.50 and 0.40, respectively; the book's mass is 0.90 kg and your downward push on it is 10 N. How much horizontal force is needed to keep the book moving at a constant speed if your hand is stationary with respect to the table?

F=ma

## The Attempt at a Solution

The given values for friction kinda threw me off but this is my attempt to it
Fa= 10 N (force applied)
Fg=mg = .90•9.8 = 8.82 N
Fn = mg+ Fa = 18.82 N
Ff = Uk•Fn = .40•18.82 = 7.528

Since it’s going at a Constant speed , it means there’s no acceleration and all the forces are equal to Each other .
So the horizontal force needed wouldn’t it be the same as the Friction force (Ff) .
The correct answer should be 12.5 N

Where did I go wrong ?

Last edited by a moderator:

haruspex
Homework Helper
Gold Member
2020 Award

## Homework Statement

Place a book flat on a table and press down on it with your hand. Now suppose the hand-book and table- book values of are 0.50 and 0.40, respectively; the book's mass is 0.90 kg and your downward push on it is 10 N. How much horizontal force is needed to keep the book moving at a constant speed if your hand is stationary with respect to the table?

F=ma

## The Attempt at a Solution

The given values for friction kinda threw me off but this is my attempt to it
Fa= 10 N (force applied)
Fg=mg = .90•9.8 = 8.82 N
Fn = mg+ Fa = 18.82 N
Ff = Uk•Fn = .40•18.82 = 7.528

Since it’s going at a Constant speed , it means there’s no acceleration and all the forces are equal to Each other .
So the horizontal force needed wouldn’t it be the same as the Friction force (Ff) .
The correct answer should be 12.5 N

Where did I go wrong ?
pay attention to the statement that your hand does not move. Something else is pushing the book sideways.

pay attention to the statement that your hand does not move. Something else is pushing the book sideways.

Oh, so I just include the friction of the hand
Ff= Uk(Fn) =.5•10N = 5
Then add both friction forces together
Okay thanks !