Which statement correctly describes the differences between positive and negative acceleration? positive acceleration describes a change in speed; negative acceleration describes no change in speed. positive acceleration describes no change in speed; negative acceleration describes a change in speed. positive acceleration describes an increase in speed; negative acceleration describes a decrease in speed. positive acceleration describes a decrease in speed; negative acceleration describes an increase in speed.

Positive acceleration describes an increase in speed; negative acceleration describes a decrease in speed.

Explanation:

Acceleration is defined as:

where

v is the final velocity

u is the initial velocity

is the time taken for the change in velocity to occur

The value of is always positive, so the sign of the acceleration depends on the numerator. More specifically, we have two situations:

- if , then it means that the final velocity is greater than the initial velocity, so the acceleration is positive and the speed is increasing

- if , then it means that the final velocity is smaller than the initial velocity, so the acceleration is negative and the speed is decreasing

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.

answer///terminator or twilight zone;