Which physical property is shown by scratching one material with another

Determine the maximum r-value of the polar equation r =3+3 cos 0

Under the action of a constant force an object accelerates at 7.8 m/s2. what will the acceleration be if (a) the force is halved? (b) the object's mass is halved? (c) the force and the object's mass are both halved? (d) the force is halved and the object's mass is doubled?

Which levels of government establish and implement educational requirements for minors