Transcript Laws of Motion

Laws of Motion
Forces: chapter 11
1st Law
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An object at rest remains at rest and an
object in motion maintains its velocity unless
it experiences an unbalanced force.
2nd Law
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The unbalanced force acting on an object
equals the object’s mass times its
acceleration:
force = mass x acceleration
F = ma
Calculate the force of…
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A block of ice with a mass of 12.5 kg being
accelerated at a rate of 3.5 m/s2
2nd Law continued…
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Or, the acceleration of an object is
proportional to the net force on the object
and inversely proportional to the object’s
mass:
acceleration = force ÷ mass
a=F÷m
Calculate the rate of acceleration...
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of a sailboat with a mass of 655 kg while it
experiences a net force of 895 N
Law of Universal Gravitation
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Newton generalized his observations on
gravity in a law now known as the law of
universal gravitation.
Mathematically, the law of universal
gravitation is stated as:
F = G (m1m2 ÷ d2)
Math Skills
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The force between a planet and a spacecraft
is 1 million newtons. What will the force be if
the spacecraft moves to half its original
distance from the planet?
Free Fall and Weight
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The free-fall acceleration of an object due to
gravity near the Earth’s surface is 9.8m/s2
Weight is equal to mass times free-fall
acceleration
w = mg
Calculate the weight of…
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A 65 kg astronaut on the surface of the
moon, where g = 1.6 m/s2
3rd Law
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For every action force, there is an equal and
opposite reaction force.
Momentum
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Moving objects have momentum.
Momentum is a quantity defined as the
product of the mass and velocity of an object.
Momentum Equation
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Momentum = mass x velocity
p = mv
Calculate the momentum of…
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a 65 kg skateboarder moving forward at the
rate of 3.0 m/s