Which of the following is described as applying force to change an object's direction or speed?

Applying force is a fundamental concept in physics and is essential for understanding motion. When force is applied to an object, it can result in a change in the object's direction or speed, which is encapsulated by Newton's second law of motion. This law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Therefore, when an unbalanced force is applied, the object will either speed up, slow down, or change direction based on the direction and magnitude of the force applied.

In this context, the term "force" encompasses various types, including gravity, tension, normal force, and friction, and all these types influence an object's state of motion. By understanding that force is the key element that leads to changes in motion, one can better grasp concepts such as acceleration, velocity, and momentum in physical science.