Question

A car moves at a speed of 36kmh−1 on a level road, The coefficient of fraction between the tyres and the road is 0.8. The car negotiates a curve of radius R. If g=10ms2 the car will skid (or slip) while negotiating the curve if value of R is

Answer 1

"coefficient of fraction"
should be behind . this is too general to be used when in physics .
There are two coefficient of fraction :
1) first coefficient of STATIC fraction.
2) coefficient of kinetic fraction .
For rotating tires against a road surface, the obvious coefficient would be KINETIC.
BUT,
in the case above , a slip or skid occurs when the static fraction force is overcome.
Therefore , 0.8 = coefficient of STATIC fraction =
$us$
the normal force of car against curved road
(assuming no banking)= mg
The static fraction force of tires against road =
mg

NOW,

As 36 km/hr =
$36 \times 1000 \div 3600$
=10 m/s
by mv^2/r =mg
=>r= (10)^2/(0.8 x 10)
=>r=12.5 m


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