A thin rectangular piece of wood floats in water. You slowly pour oil with a density equal to that of the wood on the surface of the water until the height of the oil above the water is twice the height of the piece of wood. Which statement is correct?

A. The wood floats on top of the oil, so it sticks up in the air.
B. The wood does not change its position
C. The wood sinks below the surface of the water
D. The wood is half in the water and half in the oil.
E. The wood floats in the oil just above the water.

B. The wood does not change its position

Explanation:

Since the oil has the same density as the wood there will be no buoyant force on the wood by the oil, the wood will remain in its initial position just above the water surface but below the oil surface

the force required to move the cart is divided by three or 33.33 n.

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.