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MOTION
d
s t
Average speed = change in distance change in time
S = Δd / Δt
Velocity includes speed and direction!!
Speed constant…velocity changing…acceleration changing
Δv
a Δt
Acceleration = final velocity - initial velocity final time - initial time
a = Δv/Δt
Newton’s 1st Law of Motion
An object at rest remains at rest unless acted upon by an unbalanced net force
orAn object moving at a constant velocity continues to
move at that velocity unless acted upon by an unbalanced net force
Forces4 Basic Forces: gravity, strong nuclear force, weak nuclear force, electromagnetic force
Newton’s 2nd Law of MotionAn object’s acceleration is in the same direction as the
net force acting upon it
Acceleration(m/s2) = net force(N)/mass(kg)
a = Fnet / m
Law of Universal Gravitation
Find the force of gravity between 2 objects, if masses and distance between them are known
Gravitational = (constant) x (mass1)x(mass2) force (distance)2
F = G m1m2
d2
Note force changes as mass and distance changes!
Force of Earth’s Gravity and an object’s Weight on Earth
Force of = mass(kg) x acceleration of gravity(N) gravity (9.8m/s2)
F = mg
Weight on = mass(kg) x acceleration of Earth gravity(9.8m/s2)
W = mg
An Object’s Weight on Earth is the Force of Gravity acting upon that object!!
Newton’s 3rd Law of MotionWhen one object exerts a force on a second object,
that second object exerts a force that is equal in strength, and opposite in direction
orFor every action force, there is an equal and
opposite reaction force
F1
Dir 1
F2
Dir 2
The skater throws the ball with force F1 in the direction Dir 1; The ball exerts a force F2 on the skater, who moves in the opposite direction Dir 2
Law of Conservation of Momentum
If a group of objects exerts forces only on each other, the total momentum is conserved
M3
M1 v1 M1 v1’
M2
v3
v2
M1V1 = M1V1’ + M2V2 + M3V3
WorkW(Nm) = F(N) x d(m)
d1
d2
F1
F2
How do the distances d1 and d2 compare? F1 and F2?
How does the work to move the object from floor to shelf by direct lifting compare to that by using the ramp?
Is there any advantage to using the ramp?
Mechanical Advantage
Mechanical Advantage = Force (out) / Force (in)
MA = Output Force = Lift Force (no ramp) Input Force Force with ramp
POWER
Power = rate of Energy Use= rate of Work completion
Power (Watts) = Energy (Joules) Time (s)
P = E/t = W/t