Newton’s First Law of Motion Chapter 3 Section 2 Newton’s First Law of Motion • Sir Isaac Newton (1642 – 1727) was able to state rules describing the effect of forces on motion of objects that are still true today. • These rules are known as: Newton’s Laws of Motion • Newton’s First Law of Motion is also called The Law of Inertia Newton’s First Law of Motion • An object moving at a constant velocity keeps moving at that velocity unless a net force acts on it. • If an object is at rest, it will stay at rest, unless a net force acts on it. • If an object is in motion, it will stay in motion, unless a net force acts on it. Newton’s First Law of Motion What Happens in a Crash? • Newton’s Law First Law of Motion • If you are traveling at 50 kilometers per hour and you hit a tree… What Happens in a Crash? • If you are not wearing your seatbelt… • The car is stopped by the tree and you continue to move forward at a speed of 50 kilometers per hour until you hit the dashboard, steering wheel, windshield, etc. • You would hit at the same speed you would reach if you fell from a three-story building. What Happens in a Crash? • If you are wearing your seatbelt… • The seatbelt loosens a little upon impact and will hold you. • This allows your body to be slowed down gradually and decreases the unbalanced force placed on your body. • The seatbelt could also save you from being thrown outside the car.
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