Science · Physical Science
Newton’s First Law of Motion
Reading comprehension passage and printable worksheet about Newton’s First Law — inertia and how forces affect motion — for grades 4–7.
Subject
Science
Grade Level
Grades 3–8
Resource Type
Lesson Plan
Format
Lesson + PDF
Reading Passage
Newton’s First Law of Motion
Sir Isaac Newton was one of the greatest scientists who ever lived. In 1687, he published a book describing three laws of motion that explain how and why objects move. These laws are still used today in science, engineering, and everyday life. The first of Newton’s three laws deals with inertia — the tendency of objects to keep doing what they are already doing.
Newton’s First Law of Motion states: An object at rest stays at rest, and an object in motion stays in motion with the same speed and direction, unless acted upon by an unbalanced force. In simple terms, things don’t start moving, stop moving, or change direction on their own. Something has to push or pull them to make that happen.
The property described in Newton’s First Law is called inertia. Inertia is the resistance of an object to any change in its motion. Every object has inertia — even objects at rest have inertia because they resist being set into motion. The more mass an object has, the more inertia it has. A large truck has much more inertia than a small bicycle and is harder to start moving or stop.
You experience inertia every day. When a car stops suddenly, your body lurches forward — that is inertia keeping your body in motion while the car stops. A seatbelt provides the unbalanced force that stops your body from continuing forward. When a car accelerates quickly, you feel pushed back into your seat — your body’s inertia resists the change in motion as the car speeds up.
Friction is one of the most important forces that acts against inertia in daily life. Friction between a ball and the ground slows a rolling ball until it stops. Without friction, a rolling ball would keep rolling forever, just as Newton’s First Law predicts. In space, where there is no air friction, objects really do keep moving at the same speed in the same direction for enormous distances.
Printable Worksheet
Printable PDF · 5 pages
Newton’s First Law of Motion Reading Comprehension Worksheet
Printable worksheet includes the reading passage and comprehension questions about inertia, Newton’s First Law, and how forces affect the motion of objects. Includes answer key.
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