I need help on 3 and 4 please

Acar of mass m goes around a banked curve of radius r with speed v. if the road is frictionless due to ice, the car can still negotiate the curve if the horizontal component of the normal force on the car from the road is equal in magnitude to 101) a) mv2/r b) mg/2. d) mg e) tan[v2/(eg)]

Which of the following are guidelines to follow for obtaining accurate observations

At what time will the interfering waves have an amplitudeof zero?