Chapter 2, Problem 15A

If you push a crate across a factory floor at constant speed in a constant direction, what is the magnitude of the force of friction on the crate compared with your push?

To determine

The magnitude of the force of friction on the crate as compared with the push on it.

Answer to Problem 15A

Friction will be equal to the push on the crate for the given case.

Explanation of Solution

Introduction:

When the objects move in a straight line with a constant speed, they are to be in dynamic equilibrium.

It is known that when the object is in equilibrium, then the net force on it is zero, that is,

  ${\displaystyle \sum F}=0$

And, since crate is moving with a constant speed in a constant direction, thus it is in dynamic equilibrium. Hence,

  $\begin{array}{c}{F}_{\text{push}}-F_{\text{friction}}=0\\ F_{\text{push}}=F_{\text{friction}}\end{array}$

Conclusion:

Thus, the push on the crate will be equal to the friction force on the crate if it moves with a constant speed in a constant direction.