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Unit IV: Force. Newton’s First Law and Moving Situations Per. 3, 6. Newton’s First Law. “An object moving at a constant velocity will continue moving at a constant velocity, unless acted upon by an unbalanced force.” We can include our half-statement from last time:
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Unit IV: Force Newton’s First Law and Moving Situations Per. 3, 6
Newton’s First Law “An object moving at a constant velocity will continue moving at a constant velocity, unless acted upon by an unbalanced force.” We can include our half-statement from last time: “An object at rest will stay at rest unless acted upon by an unbalanced force.”
This can be reformulated as having four logical implications: • If an object is moving with a constant velocity. . . Then the forces on it must be Balanced What is the reverse of this statement? 2. If the forces on an object are balanced. . .
And if the forces on an object are not balanced? Then the object’s velocity is changing said another way, it must be accelerating it accelerates (speeds up or slows down) in the direction of the unbalanced Force. 4. Reverse – If the Forces on an object are not balanced. . .
Why is this such a BIG DEAL? • Newton – perhaps the biggest single name in physics • Law not formulated until the 1600’s • Why was it so difficult to figure out? • What usually happens when something is moving?
Add to your Force Inventory • Kinetic Friction Force • Identify every force acting on the system
Half of Newton’s First Law • If an object is at rest, the Forces acting on that object are balanced • How can we judge whether forces are balanced?
Remember: • Friction Force parallel to surface, opposes motion • Normal Force perpendicular to the surface exerting the force • Tension Force along the length of the rope or string.
