A person is pushing a box across a table. The measured forces on the box are 10N, 14N, -7N, -10N. Which force is represented by -7N?

force of friction
normal force
force of gravity
push force

Americium-241 undergoes fission to produce three neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 1.8 neutrons per fission event, which will be effective at achieving a critical mass? check all that apply. remove a deflective shield surrounding the sample. remove absorbent material mixed in with the sample. compress the sample of americium-241.