Which of the following best describes an action-reaction pair?

a. the moon pulls on earth, and earth pulls back on the moon.

b. a bed sits on the floor, and earth's gravity pulls down on the bed.

c. a television pushes down on a shelf, and the shelf pulls the television down.

d. you kick a wall, and the wall pulls on your foot.

The Moon Pulls on Earth, and Earth pulls back on the moon.

Explanation:

Newton's third law of motion describes action and reaction forces. It tells that an object applies an action force on another and another object also exerts a reaction force on the first object. Both the action and reaction forces are of equal magnitude but they act in opposite direction.

Option (A) is an example of action- reaction pair i.e. "The Moon Pulls on Earth, and Earth pulls back on the moon". Earth exerts a gravitational force on the Moon. The gravitational pull of the Earth on the Moon is much more stronger than the pull of Moon on the Earth.

So, the correct option is (A).

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.