An object with a mass of 20kg changes position as a function of time according to the expression r = 4t ^ 2i + 5j, where r is expressed in meters and t in seconds. a) What is the expression of velocity as a function of time of the object? b) What is the expression of acceleration as a function of time of the object? c) What is the position, velocity and acceleration of the object at t = 3s? d) What is the force of the object and in what direction is it heading (east, north, west or south)?

the first step is making objective observations.

they have to be based on a certain event and can be confirmed by others if it is right or not.

the higher the current the higher the mag field around it the higher the influence on the compass

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.