Gravitational attraction between spheres

A brass sphere is placed 2m from another brass sphere of mass 5kg. The mutual gravitational attraction between these spheres is measured to be 7X10^-9N. Find the mass of the first sphere.

Applying the uncertainty principle to a moving bullet.

A bullet of mass 25gm is moving with a velocity of 400m/s. The speed is measured accurately up to 0.02%. Calculate the certainty with which the position of the bullet can be located.

Radiations

PART ONE: The radiations of radioactive nuclides: A) affect the emulsion on a photographic film B) ionize surronding air molecules C) make certain compounds fluoresce D) do all of these PART TWO: The subatiomic research that can be conducted using particles and radiations from naturally radioactive substances is limited becuase the radioactive emissions: A) are highly accelerated B) have insufficient energy C) have great penetrating power D) have an easily controlled rate

Gravitational forces

A 5kg mass is 4m away from a 10kg mass. Find the gravitational force on the 5kg mass due to the other mass. What is the force on the 10kg mass due to the 5kg mass? If both masses are free to move, what are their respective accelerations?

Electrons

PART ONE: According to the Bohr model of the atom, an electron cannot move from a lower energy orbit into a higher energy orbit: A) abruptly B) spontaneously C) unless it gains extacly enough energy D) unless it loses exactly enough energy PART TWO: No two electrons in an atom can have the same: A) orbit B) spin C) angular momentum in a magnetic field D) set of quantum numbers