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Types of Forces and Gravitational Force. 4.6 and 4.7. 4.6 Types of Forces. Some common forces Gravitational Force Normal Force Frictional Force Tension Force. Fundamental Forces. Unique forces All other forces are forms of these Gravitational Force Gravity Strong Nuclear Force
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Types of Forces and Gravitational Force 4.6 and 4.7
4.6 Types of Forces • Some common forces • Gravitational Force • Normal Force • Frictional Force • Tension Force
Fundamental Forces • Unique forces • All other forces are forms of these • Gravitational Force • Gravity • Strong Nuclear Force • Keeps nucleus of atoms together • Electroweak Force • Electricity, Magnetism, and Weak Nuclear Force (radioactivity)
Nonfundamental Forces • Except for Gravitational all the common forces are nonfundamental • Others related to electromagnetic (electroweak) forces
4.7 Gravitational Force • Why does g = 9.80 m/s2? • It’s related to Newton’s Law of Universal Gravitation
Newton’s Law of Universal Gravitation • Every particle in the universe exerts a force on every other particle • G = 6.673 x 10-11 N m2/kg2 • m1 and m2 are the masses of the particles • r = distance between the particles
Newton’s Law of Universal Gravitation for Nonparticles • Using calculus – apply universal gravitation for bodies • Estimate (quite precisely) • Assume bodies are particles based at their center of mass • For spheres assume they are particles located at the center
Example 1 • What is the gravitational attraction between a 75-kg boy (165 lbs) and the 50-kg girl (110 lbs) seated 1 m away in the next desk? • Fg = 2.5 x 10-7 N • = 2.6 x 10-8 lbs of force
Weight • Gravitational Force the earth exerts on an object • Unit: Newton (N) • Remember!!! • Weight is a Force
Relationship Between Weight and Mass • Weight force of gravity on object • Force • Mass measure of inertia of object • Amount of matter present
Another Formula for Weight • r is usually RE • So g = 9.80 m/s2
Example 2 • What is the weight of a 90 kg person? • W = 882 N • What is the mass of that person on the moon (g = 1.63 m/s2)? • m = 90 kg • W = 147 N
Practice Work • 115 #CQ10, 12, P18 – 21, 23, 29 • Total of 8 Problems