Transcript PS2MotionForces

MOTION
Average speed = change in distance
change in time
d
s
t
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
or
An object moving at a constant velocity
continues to move at that velocity
unless acted upon by an unbalanced net
force
Forces
4 Basic Forces: gravity, strong
nuclear force, weak nuclear force,
electromagnetic force
Newton’s 2nd Law of Motion
An 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 =
gravity(N)
mass(kg) x acceleration of
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 Motion
When one object exerts a force on a
second object, that second object
exerts a force that is equal in
strength, and opposite in direction
or
For every action force, there is an
equal and opposite reaction force
F2
Dir 2
F1
Dir 1
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
v3
M3
M1
v1
M1
v1’
M2
v2
M1V1 = M1V1’ + M2V2 + M3V3
Work
W(Nm) = F(N) x d(m)
F1
d1
F2
d2
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