A box with a mass of 5 kg accelerates its speed in a straight line, increasing it from 5 m/s to 8 m/s, due to the application of an external force acting for a duration of 2.0 s. Calculate the average strength of this force.

Which body is in equilibrium? (1) a satellite orbiting earth in a circular orbit (2) a ball falling freely toward the surface of earth (3) a car moving with a constant speed along a straight, level road (4) a projectile at the highest point in its trajectory