If it actually hits the ground with a speed of 8.50 m/s , what is the magnitude of the average force of air resistance exerted on it?

According to newton’s first law of motion, which force is expected to cause a body to accelerate?

An object weigh 40n in air ,weigh 20n when submerged in water,and 30n when submerged in a liquid of unknown liquid density.what is the density of unknown of liquid?

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?