A boy runs in a 125-m race from rest. In the first 5 seconds, he increases his speed with a constant acceleration of 2.0 m/s2. He then maintains this speed for the rest of the run. Calculate the total
time taken for the boy to finish the run.

Assuming starting at zero velocity: at 4 seconds speed is 8 m/s (2m/s^2 * 4 seconds) and distance is 16 m (average speed is 4 m/s * 4 seconds). The remaining 84 meters (at 8 m/s) takes 10.5 seconds.

So total time to run 100 meters is 14.5 seconds.

Explanation:

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

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.