Answer:
Speed = 9.9 m/s
Step-by-step explanation:
Given:
Coefficient of static friction is,

Radius of the curve,
m
Let the speed that has to be reached be
m/s.
In order to avoid sliding while making a turn, the frictional force provides the necessary centripetal force.
We know that, frictional force acting on a body is given as:
(
as there is no vertical motion)
Also, from the definition of centripetal force,

On equating the above two equations, we get

Now, plug in 0.25 for
, 9.8 for
and 40 for
.

Therefore, speed of the car has to be slowed down to minimum of 9.9 m/s in order to avoid sliding while making a turn.