An athlete starts running from rest such that he covers a distance of 5mm in 0.50s with a constant change in velocity per unit time . when will he reach the finish line, if he is running a race of 50m?

50 s

Explanation:

Given:

Δx = 0.005 m

v₀ = 0 m/s

t = 0.50 s

Find: a

Δx = v₀ t + ½ at²

0.005 m = (0 m/s) (0.50 s) + ½ a (0.50 s)²

a = 0.04 m/s²

Given:

Δx = 50 m

v₀ = 0 m/s

a = 0.04 m/s²

Find: t

Δx = v₀ t + ½ at²

50 m = (0 m/s) t + ½ (0.04 m/s²) t²

t = 50 s

he . if i may ask what i your question exactly?

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.