Yesterday, the author has lifted a cup to drink from it and threw a ball for the dog. In the case of the cup, they applied upward force to the cup at a constant rate until it reached the necessary height, at which point the pressure was reduced to let it stay in place. The reaction force was applied to their hand, pushing it down both while the cup was being raised and when it was still. Lastly, the cup accelerated at the beginning of the movement and decelerated at its end, maintaining a constant speed in the middle. In the case of the ball, the author performed a motion similar to quarter-circle with their arm, with the force pointed in the same direction (after accounting for gravity). As in the above case, the reaction force was opposed to the force of the throw. The ball’s acceleration was initially pointed in the same direction as the hand’s movement but moved to point nearer the middle of the semicircle described above as its speed rose.
The easiest way to know that force is being applied to one is through the sense of touch. When one is being pushed or pulled in a specific spot, they will know it because they will feel the force on their skin. It is more difficult to see when the pressure is applied to the entire body, such as when one is in a car, but acceleration can still be felt. Another way to know would be to use one’s sight. If a person can see that they are moving, they can usually safely guess that some force is being applied to them to make them do so.