# Homework Help: Dynamics question

1. Jan 17, 2010

### maccha

If a block of wood, initially at rest, is being pushed across the floor (force of friction is not negligible), when the person stops pushing the block, will it immediately come to rest, slow down to a stop or keep going?

I assume it would immediately come to a stop but I don't really know how to explain this in terms of physics concepts. Is it because it's "natural state" is rest and so when nothing is exerting a net force on it it will revert back to this?

2. Jan 17, 2010

### mg0stisha

It's incorrect in this case to say that once the person stops pushing on the block that there is no net force on the block. look back to one of the things you said in the initial description of the situation. what would cause the block to have a force acting on it after the person stops pushing?

3. Jan 17, 2010

### vela

Staff Emeritus
What does Newton's first law tell you?

You might find it helpful to think about "extreme" cases. For instance, say there was friction but it was nearly frictionless, like an ice skater on ice. When the skater stops pushing herself forward, does she come to a stop immediately?