Why couldn't mendeleev organize the entire periodic table during his research? question options: the elements showed no periodic properties. the atomic number was unknown at the time. some elements were undiscovered at the time. the atomic mass was unknown at the time.

Crowbar of 5 metre is used to lift an object of 800 metre if the effort arm is 200cm calculate the force applied

Which statement is true? a. kepler's laws apply only to the motion of earth. b. kepler's laws can be used to predict eclipses. c. kepler's laws are true for a central force that is directly proportional to distance. d. kepler's laws can be deduced from newton's laws of motion and gravity.

Distinguish between linear momentum and angular momentum