Final answer:
Devices that change the direction or size of a force are known as simple machines, which include levers, pulleys, and others. Friction is considered an external force according to Newton's first law of motion, and the unbalanced forces, or net force, dictate the object's motion as per Newton's second law.
Step-by-step explanation:
The devices that change the direction or size of a force are known as simple machines. These machines include levers, pulleys, inclined planes, wheels and axles, screws, and wedges. For example, a pulley can change the direction of the force applied to lift a heavy object, making it easier to elevate. A lever, on the other hand, can increase the force exerted on an object, thereby allowing you to lift heavier loads than you normally could.
In terms of the concepts you've been studying, when discussing Newton's laws of motion, it's important to distinguish between different types of forces. Friction is an example of an external force that can either oppose or facilitate the motion of objects. According to Newton's second law, a net force, which is a combination of all the forces acting on an object, results in a change in motion – an increase or decrease in velocity or a change in direction.
For instance, if only two forces are acting on an object, force A to the left and force B to the right, and if force B is greater than force A, the object will move to the right owing to the unbalanced or net force acting on it.