# 160_6_5_work_COMPLETE.pdf - 6.5 Force & Momentum Newton’s...

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6.5 Force & MomentumNewton’s First Law of Motion:objects continue to move in a state of constant velocity (or remain at rest)unless acted upon by an external forceForcedescribes the (rate of) change in the momentum of an object caused (by some other object).Momentumpis the product of massmand velocityvof an object.p=mvThinkaboutit:To change the momentum of an object (of constant mass) requires you change its velocity. This requiresforce. The force required is proportional to the mass of that object.Thinkaboutit:
6.5 Force & MomentumNewton’s Second Law of Motion:Force = mass×accelerationF=m·aIf mass iskgand acceleration ismeters/sec2, the force has unitskg·m/s2, which is called a “newton,”N.Example 1)Accelerationadue to gravity isg= 9.8m/s2. So on a 5 kg object, the force of gravity is:While 1 kg2.2 pounds,weight in poundsactually refers to the force of gravity on an object. Weight isnot mass. Weight is force from gravity.Example 2)Accelerationadue to gravity isg= 32ft/s2. On a 5 lb object, the force of gravity is:In the British FPS system (foot-pound-sec), 1 pound (of gravitational force) corresponds to132“slug” ofmass (1 slug = 14.5939 kg). To use mass in theF=m·aequation, you would use slugs, not pounds.
6.5 Work & EnergyWhen a forceFcauses an object to move some distanced, we sayenergyhas been transferred to the objectthroughwork.

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Term
Spring
Professor
HERSH
Tags
Mass, Work Energy
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