# Common forces in mechanics

1. Jan 12, 2012

### mr newtein

two blocks are connected by string if i pull a block,then block(it will transmit force) will also pull string then,string will also pull block (a& r pairs)forces on block are by me and by string of equal magnitude than why is block accelerating

2. Jan 12, 2012

### nasu

The force from the string on the block is not necessarily equal to your force on the block.

3. Jan 12, 2012

### Staff: Mentor

common layman's usage is:

I apply a force on a block and it moves.

but for physics you need to think this way:

I apply a force (f=ma) on a block of mass m and it accelerates (no friction case).

in the real world with friction:

I apply a force (f=ma) on a block of mass m and it accelerates to some constant
speed because the frictional force increases with increasing speed and opposes the
force Im applying.

4. Jan 12, 2012

### mr newtein

i am not getting it

5. Jan 12, 2012

### mr newtein

why? it because,the block may not transferring all force i am applying.