Before 1960, people believed that the maximum attainable coefficient of static friction for an automobile tire on a roadway was μs = 1. around 1962, three companies independently developed racing tires with coefficients of 1.6. this problem shows that tires have improved further since then. the shortest time interval in which a piston-engine car initially at rest has covered a distance of one-quarter mile is about 4.43 s. ]

This problem is looking for the minimum value of μs that is necessary to achieve the record time. To solve this problem:

Assuming the front wheels are off the ground for the entire ¼ mile = 402.3 m, the acceleration a = µs·9.8 m/s².

For a constant acceleration, distance = 402.3

m = 1/2at^2 = 804.6 m / (4.43 s)^2 = a = µs·9.8 m/s^2

µs = 804.6 m / (4.43s)^2 / 9.8 m/s^2 = 4.18

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this