# Is the friction "reaction force"?

1. Mar 31, 2015

### LogU16

Hello, members.

When a vehicle moves on the road, it applies a force to the road (action force according to the Newton's 3rd law), road also applies an equal and opposite force on the wheels of the vehicle to cause it to move forward.

My question is, is this reaction force frictional force? Normally we say that vehicles move on the road due to friction, can we call it (friction) as a reaction force (provided by the road to the vehicles)?

I'm bewildered, need your kind help.

Many many thanks.

2. Mar 31, 2015

### rcgldr

The tires on the car exert a backward frictional force onto the pavement, coexistant with the pavement exerting a forwards frictional force onto the tires. As for reaction, the earth's surface accelerates backwards at a very tiny rate, and the car itself may be acelerating, the car is accelerating air forwards, and internal drag forces are converting mechanical energy into heat.

3. Apr 1, 2015

### Philip Wood

Action and reaction are unfortunate terms, because they suggest that one (action) is in some sense prior to the other. This is not so. In Newtonian physics forces come in pairs, so there is friction between the tyre and the road: the tyre exerts a ('backwards') force on the road, and the road exerts a 'forward' force on the tyre (assuming the axle is being rotated by another agency). Both forces (tyre on road and road on tyre) are frictional forces; they are different aspects of the same interaction.