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Semester Exam Review
Math and Metrics
Sig Fig Rules:
505 – zero is significant
500 – zeroes not significant
0.05 – zeroes not significant
5.00 – zeroes significant
0.0500 – only zeroes at the end are significant
Most commonly missed rule: zeroes that are after
the decimal and are final zeroes are significant
Math and Metrics
Be able to convert (m/skm/h) (mcm), etc
Be able to convert from standard form to
scientific notation and vice versa
Example: change 0.0002490 to scientific
notation
Example: change 4.12 x 106 to standard form
Linear Motion
What is the distance?
What is the displacement?
Speed vs Velocity
• Speed = scalar
• Velocity = vector
S = total distance / total time
V = displacement / total time
Acceleration
• The rate of change of velocity
• All acceleration we have studied has been
constant
• + v and + a = speeding up
• + v and – a = slowing down
• - v and + a = slowing down
• - v and – a = speeding up
a = v f - vi
t
d = vit + ½ at2
vf2 = vi2 +2ad
Free Fall
• An object is considered in free fall when it is
moving only under the influence of gravity.
• An object that is thrown up in the air is in free
fall (even when it is moving up).
• When an object is in free fall, its acceleration
is -9.8 m/s2.
• The entire time the object is in free fall its
acceleration is -9.8 m/s2 even when the object
is moving up.
Graphing
• Know how to draw graphs of:
d vs t; v vs t; a vs t
For object:
At rest
Constant speed
Speeding up
Slowing down
Dropped
Thrown up and comes back down
Graphing
• Be able to identify what v vs t graph belongs
to what d vs t graph
Vector Addition
Vectors
Know how to add vectors in the same direction,
in opposite directions and at right angles.
Be able to find components of a vector (i.e. sides
of a triangle)
Vectors
S = d/t can be used with vectors
You must match up speed and distance
Projectiles
• Projectiles move at constant velocity in x
direction
• Projectiles have acceleration -9.8 m/s2 in y
direction
• Time for a falling object is the same as time
for an object to hit the ground if fired
horizontally.
Forces
• Newton’s 1st Law: Object in motion stays in
motion, object at rest stays at rest UNLESS
acted on by an outside force (also called law
of inertia)
• Newton’s 2nd Law: Fnet = ma
• Newton’s 3rd Law: For every force there is an
equal and opposite force
Forces
• Force is not needed to maintain motion.
• Object with zero net force is in equilibrium
• Object in equilibrium will have no change in
its motion (either at rest or in motion at a
constant speed)
• Inertia is not a force. It is the tendency of an
object to resist a change in its motion.
Forces
• Inertia is directly proportional to mass (more
mass, more inertia)
Forces
• Problem solving:
Basic: net force given? Fnet = ma
Advanced: multiple forces acting (i.e. tension
and weight, or Fapp and Friction) draw FBD
and write equations (U-D = may) (R-L = max)
Force
• More Problem Solving
Equilibrant force: use pythagorean theorem to
find resultant force equilibrant force is same
value 180 degrees in other direction
Momentum
• P = mv
• J = Ft
• Momentum is changed when an impulse acts
on an object.
• The impulse is equal to the change in
momentum.
• Ft = mΔv
Momentum
• Vector quantity
• Always conserved in a closed system (no
outside forces presenti.e. friction)
Momentum
• Consequence of Impulse-Momentum
Theorem: if time of collision is extended, force
will decrease.
• Extending time has NOTHING to do with the
change in momentum, also can’t change the
value of impulse.
Momentum
• Inelastic: objects collide and stick together
• Elastic: objects collide and bounce apart
• Momentum is conserved in both types of
collisions
Concept Questions
• When you do throw that bowling ball while
standing on the pond:
How does your final velocity compare to that of
the ball?
How does your final momentum compare to
that of the ball?
Assume no friction
Ans: The ball has a greater velocity, you have
equal momentum