Compare the movement of four cars. Car A covered a distance of 60 km in 1hr. Car B covered a distance of 30 km in 30 minutes. Car C covered a distance of 20
km in 15 minutes, Car D covered a distance of 10 km in 7 minutes, which car had
the highest velocity?"

car D

Explanation:

1) before to compare all the values of the velocities, they must be in the same units of measurement. It means:

for car A: V=60km / 1h=60km/h;

for car B: V=30km / 0.5h=60km/h;

for car C: V=20km / 0.25h=80km/h;

for car D: V=10km / (7/60)h≈85.7km/h.

2) according to the values calculated in item 1 the car D had the highest velocity.

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.