An object is suspended by a string from the ceiling of an elevator. If the tension in the string is equal to 25 N at an instant when the elevator is accelerating downward at a rate of 2.0 , what is the mass of the suspended object

By Newton's second law, the net force on the object is

∑ F = T - mg = - ma

where

• T = 25 N, the tension in the string

• m is the mass of the object

• g = 9.8 m/s², the acceleration due to gravity

• a = 2.0 m/s², the acceleration of the elevator-object system

Solve for m :

25 N - m (9.8 m/s²) = - m (2.0 m/s²)

==>   m = (25 N) / (9.8 m/s² - 2.0 m/s²) ≈ 3.2 kg

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.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue