Africtional force f provides the centripetal force as a car goes around an unbanked curve of radius r at speed v. later, the car encounters a similar curve, except of radius 2r, and the driver continues around this curve at the same speed in order to make this second curve, the frictional force on the car must be equal to

The friction force is reduced to half of the initial

Explanation:

This is a problem of Newton's second law, let's write the equation for the two cases presented

R radius curve

   fr = m a

Where a is the centripetal acceleration

   a = m v2 / R

   fr = m v2 / R

2R radius curve

    fr2 = m v2 / (2R)

    fr2 = ½ (m v2 / R)

    fr2 = ½ fr

    fr2 / fr = 1/2

The friction force is reduced to half of the initial

b

explanation: