What is the largest mountain free land area in europe it stretches 2000 miles?

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

Why do different substances have diffrent properties

Suppose that three astronomical objects, 1, 2, and 3 are observed to lie on a line, and the distance from object 1 to object 3 is d. object 1 has four times the mass of object 3, and seven times the mass of object 2. find the distance between objects 1 and 2 for which the net force on object 2 is zero.