Why can't cars be constructed that can magnetically levitate in Earth's magnetic field? a. The current needed would be excessive.
b. The current within the car must flow in a complete circuit, about half Of which would exert forces against levitation.
c. Magnetic forces are always very weak.
d. Earth's magnetic field is in the wrong direction.

Aperson gives a shopping cart an initial push along a horizontal floor to get it moving, and then lets go. the cart travels forward along the floor, gradually slowing as it moves. consider the horizontal force(s) on the cart while it is moving forward and slowing. which of the following statements is correct? (a) both a forward and a backward force are acting on the cart, but the forward force is larger. (b) only a forward force is acting which diminishes with time. (c) both a forward and a backward force are acting on the cart, but the backward force is larger. (d) only a backward force is acting, no forward force.