An object ob 2 kg mass is initially at rest on the ground. then, the object is pulled up by a 20N force in 4s before it is finally released. the maximum height that the one object can reach is ...

Answer 1

Remember that a weight force Mg = 19.6 N is also acting on the object in the opposite direction

While being pulled up, it accelerates at a rate
a = (F-M*g)/M = (20-19.6)/2 = 0.2 m/s^2
Its final velocity at release will be
a*t = 0.8 m/s.

From that release velocity, you can compute the height that it rises after release. It will acquire additional height (about 1.6 m) while being pulled