(8) Forces-Newton's 1st and 2nd Laws

# (8) Forces-Newton's 1st and 2nd Laws - Lecture 8 Forces...

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Unformatted text preview: Lecture 8 Forces: Newton’s First and Second What is a force? What is a force? It’s a pull or a push. It has a magnitude and a direction F r F r Forces are vectors! Types of forces Types of forces 1. Contact forces:- Gravitational- Electric and Magnetic- Weak force (important in subatomic world)- Strong force (important in subatomic world)- Normal force (always perpendicular to contact surface); it’s the basic “push”- Tension (force through a string, cable, rope, etc): it’s the basic “pull”- Friction (appears when two surfaces slide or try to slide one against the other) 2. Action at distance or non-contact forces : (The fundamental forces of Nature!) Newton’s Three Laws Newton’s Three Laws 1. Any object remains at rest or in motion along a straight line with constant speed unless acted upon by a net force. 3. Forces occur in pairs: For every force (or action) there is an equal but opposite force (or reaction) on B by A on A by B F F = - r r 2. net all F F ma = = r r r Newton’s First Law Newton’s First Law Any object remains at rest or in motion along a straight line with constant speed unless acted upon by a net force DEMO: Air table This law tells you what happens in the absence of any force, for instance in outer space ACT: Snapped string ACT: Snapped string A small ball attached to the end of a string moves in horizontal circles on a frictionless table as shown below. If the string snaps, what will be the trajectory of the ball?...
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(8) Forces-Newton's 1st and 2nd Laws - Lecture 8 Forces...

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