Final answer:
A moving object will continue to move at a constant speed in a straight line if no force is applied, as stated by Newton's first law, otherwise known as the law of inertia.
Step-by-step explanation:
Yes, it is true that if no force is applied to a moving object, it will continue to move with a constant speed and in a straight line. This concept is encapsulated by Newton's first law of motion, also known as the law of inertia. Newton's first law asserts that every object will continue to be in a state of rest, or move at a constant speed in a straight line unless it is compelled to change by an outside force. Therefore, in the absence of external forces, such as friction or air resistance, an object's velocity will remain constant.
For example, imagine a hockey puck sliding across a frictionless ice surface. If there are no external forces like friction or air resistance acting on the puck, it will continue to slide with the same speed in the same direction indefinitely. This is a demonstration of inertia, which is directly related to an object's mass, indicating that more massive objects have greater inertia.
It is important to note, however, that in real-world situations, external forces like friction are almost always present, which is why objects do not maintain their motion indefinitely. Nevertheless, Newton's first law provides a crucial foundation for understanding the principles of motion when external forces are negligible or absent.