Generally such problems include sentences such as “Assume their velocity to be constant” and “They are traveling in a straight line” to avoid ambiguity that could confuse the students into thinking the problem is a lot more complicated than it actually is supposed to be. (and to prevent students from claiming afterwards that there could be more than one solution or that there is no knowable solution and that therefore the problem is invalid and should therefore not count towards the test’s grade)
Generally such problems include sentences such as “Assume their velocity to be constant” and “They are traveling in a straight line” to avoid ambiguity that could confuse the students into thinking the problem is a lot more complicated than it actually is supposed to be. (and to prevent students from claiming afterwards that there could be more than one solution or that there is no knowable solution and that therefore the problem is invalid and should therefore not count towards the test’s grade)