Consider a coin which is tossed straight up into the air. After it is released it moves upward, reaches its highest point and falls back down again. Air resistance can be neglected. What force acts upon the coin when it is at its highest point?
a. Force acting up and increasing
b. Force acting up and constant
c. Force acting down and decreasing
d. Force of zero
e. Force acting down and increasing
f. Force acting down and constant
g. Force acting up and decreasing
f. Force acting down and constant
This force is gravity - mg
To determine the force acting upon the coin when it is at its highest point, we need to consider the forces acting on the coin throughout its motion.
When the coin is tossed straight up into the air, the two main forces acting on it are gravity and the upward force exerted by the person tossing it. Initially, the person exerts a force greater than gravity to overcome its weight and give it an upward acceleration.
As the coin moves upward, the force acting on it decreases gradually due to the acceleration of gravity pulling it down. At the highest point of the coin's trajectory, its velocity becomes zero for a brief moment before it starts descending.
At this highest point, the coin's acceleration due to gravity is still acting downward, but its velocity is zero. According to Newton's second law of motion (F = ma), when the velocity is zero, the net force acting on an object is also zero.
Therefore, the correct option would be:
d. Force of zero