A) What type of friction acts on a car slowing down on the road? Neglect air resistance. * static

sliding

rolling

fluid

b) What two types of force act on a skydiver with its parachute open? *

sliding friction and applied force

rolling friction and air resistance

gravity and air resistance

c) What two forces are acting on a book at rest on a table? *

gravity and sliding friction

push force and sliding friction

gravity and normal force

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

→

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

i believe the answer is three water molecules