Why gaps are left between rails while laying railway tracks

James is trying to prove newton's 2nd law of motion. he tries to move four different objects with different masses, shapes, and sizes from point a to point b. the objects are a toy car, a car, a refrigerator, and a kitchen table. after some experimentation, he finds that force is dependent on the mass of the object, rather than it's size or shape. the object that takes the most force to move is the

How can you increase the strength of an electromagnet?

Which of the following is not a transverse wave? a) soundb) lightc) radiod) all of thesee) none of these