# I need help in finding correct Coefficient of friction

1. Oct 2, 2013

### akki2063

A road vehicle equipped with mechanical wheel brake e.g drum or disc brake ,driving at a speed of 100Km/hr is braked to a stand still with a deceleration of 1G (3.2m/sec^2),How large must be the coefficient if friction between wheel and road at least be to enable that.

Options:

1)At least 1.
2)0.5
3)2

2. Oct 2, 2013

### Mentz114

The force exerted on the truck when the brakes come on ( and lock the wheels) is mg, g=3.2ms-2 and m is the trucks mass.

Can you calculate the force provided by the friction in terms of the coefficient of friction ?

(Incidentally the acceleration on the Earth's surface is about 9.7ms-2, not 3.2)

Last edited: Oct 2, 2013
3. Oct 2, 2013

### Staff: Mentor

Check your PMs. You *must* show your efforts before we can provide tutorial help. That is in the PF Rules (see the top of the page under Site Info).

4. Oct 2, 2013

### SteamKing

Staff Emeritus
I don't know where you got g = 9.7 m/s^2, but there is a different and more precise figure defined:

http://en.wikipedia.org/wiki/Standard_gravity