# I Car acceleration on concrete and on asphalt

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1. Jun 13, 2017

### ChessEnthusiast

Today I've come across the statement that the coefficient of static friction of rubber tires on asphalt is bigger than that of tires on concrete. Does it mean that the maximal acceleration a car can attain on asphalt will be greater than that on concrete?

My assumptions: 1)The force of friction is the force that "drives" the car forward
2) Asphalt gets deflected under the wheels more than concrete does

2. Jun 13, 2017

### BvU

Yes.
No. But it prevents the wheels from useless spinning
Don't think so, not that it matters.It's probably just a bit rougher on the proper scale

3. Jun 13, 2017

### ChessEnthusiast

What then is the force that drives the car?

4. Jun 13, 2017

### jbriggs444

The force of friction of asphalt on rubber tires.

The force of friction of rubber tires on asphalt acts on the asphalt. The force of friction of asphalt on rubber tires acts on the tires. Newton's third law in action.

Of course, that frictional force from the asphalt is merely applied to the tires. The force of tires on rims is what moves the rims. The force of rims on lug nuts drives the hubs. The force of hubs on axles drives the axles, etc, etc. And the torque produced by the engine is what allows all of this to persist for more than a millisecond or two.

5. Jun 14, 2017

### A.T.

Depends on the car its loading. In some cases it might not matter, because traction is not the limiting factor, but rather engine power, torque and transmission.

Statements involving scare quotes are always "true".

6. Jun 14, 2017

### sophiecentaur

The problem is that people tend to think of Friction as a 'bad' Force that only spoils our lives. That accounts for a lot of confusion. It's just a name and not a value judgement. If we say it's Friction that causes a force then we can allow ourselves to admit it may be actually useful. (After all, without it, we would not be able to stand up!!)

7. Jun 14, 2017

### A.T.

Stand up, or start walking?

8. Jun 14, 2017

### Nidum

Might be true with prepared dead smooth road surfaces but in reality the actual coefficients of friction will depend on a multitude of detail factors .

9. Jun 14, 2017

### gmax137

Actually the asphalt can deform a lot more than concrete. In many cities you will notice the bus stops are concrete while the rest of the street is asphalt. This is done because the bus pulling away from the stop will ripple the asphalt.

10. Jun 14, 2017

### jbriggs444

If you are in the road maintenance business, a little bit of deflection multiplied by many bus trips adds up. If you are driving the bus, the deflection of the road is negligible.

11. Jun 14, 2017

### BvU

Let me make this worse : what force "drives" a rowing boat ?