A block of material of volume 20cm³ and density of 2.5gcm³suspended from a
spring balance with half of the volume of the block immersed in water. What is the
reading of the spring balance?

0.4 N

Explanation:

Draw a free body diagram of the block.  There are three forces: weight force mg pulling down, buoyancy force ρVg pushing up, and tension force T pulling up.

Sum of forces in the y direction:

∑F = ma

T + ρVg − mg = 0

T = mg − ρVg

T = g (m − ρV)

Plugging in values:

T = (9.8 m/s) ((2.5 g/cm³ × 20 cm³) − (1 g/cm³) (10 cm³)) (1 kg / 1000 g)

T = 0.392 N

Rounded to one significant figure, the reading of the spring scale is 0.4 N.

all of the answers are correct.

falsification is manipulating research materials, equipment, or processes or changing or omitting data or results such that the research is not accurately represented in the research record. plagiarism is the appropriation of another person's ideas, processes, results, or words without giving appropriate credit.

explanation:

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.