When a rocket is launched into the sky, what force must it overcome? a) friction b) gravity c) lift d) thrust

B) gravity

Explanation:

For a rocket to launch, it must overcome the force of gravity acting on it. For this, it produces an upward force (thrust) that "fights" against the force that is pulling it downward (gravity).

To produce the buoyant force, the rocket engines produce combustion gases, usually using liquid hydrogen as fuel and liquid oxygen as the oxidizer, these gases are expelled by the rocket nozzles, pushing against the upper wall of the nozzles. The relationship between the forces can be summed up by Newton's third law, in which every action causes a reaction of equal force and direction and opposite direction, the gases are expelled with such a force that it exceeds the force of the rocket, propelling it upwards .

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.

trig 15.3 cos