Aparachutist of mass 75kg descends with an acceleration of 8 m/s2. what is the upward force exerted by the air on the parachutist?

Which situation will produce the greatest change of momentum

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?

Estimate of the number of stars in our galaxy