REVIEW FOR MID TERM 1

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REVIEW FOR MID TERM 1
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SI CGS BE
Length Meter (m) Centimeter (cm) Foot (ft)
Mass Kilogram (kg) Gram (g) Slug (sl)
Time Second (s) Second (s) Second (s)
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English ? S.I.

• 1 inch 2.540 cm (centimeter 1/100 meter)
• 1mile 1.609 km (kilometer 1000 meters)
• 1 pound 454 g (gram)
• 1.06 quart 1 L (litre)

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Components Of Vectors A Ax Ay
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Using Components To Add Vectors
Cx Ax Bx Cy Ay By
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Vav,x (x2-x1)/(t2-t1) ?x/?t SI unit m/s
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Average Acceleration
aav,x (v2x v1x) / (t2 - t1) ?vx / ?t SI
unit m/s2
Instantaneous Acceleration ax lim (?vx/?t)
?t 0 SI unit m/s2
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Cars Accelerating or Decelerating
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Constant-Acceleration Equations of Motion
Variables Related Equation
Velocity, time, acceleration vx v0x axt
Position, time, acceleration x x0 v0xt (½ )axt2

Velocity, position, acceleration vx2 v0x2 2ax(x x0) v0x2 2axDx
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Constant-Acceleration Equations of Motion in
Two-Dimensions

vx v0x axt vy v0y ayt
x x0 v0xt (½ )axt2 y y0 v0yt (½ )ayt2

vx2 v0x2 2ax(x x0) vy2 v0y2 2ay(y y0)
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Equations of Motion for projectileax 0m/s2
ay -9.81m/s2

vx v0x axt vy v0y ayt
x x0 v0xt (½ )axt2 y y0 v0yt (½ )ayt2

vy2 v0y2 2ay(y y0)
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Determination of key itemsfor projectiles

• x (vocos ?o)t
• ? tan-1(vy/vx)
• y (vosin ?o)t - ½gt2
• vx vocos?o
• vy vosin?o- gt

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R F1 F2 F3 .. S F, (resultant, and
vector sum, of forces) Rx S Fx ,

Ry S Fy (components of
vector sum of forces) Once we have the
components Rx and Ry, we can find the magnitude
and direction of the vector R.
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Newtons First Law Figure 4.7

• Objects at rest tend to stay at rest and objects
  in motion tend to stay in motion in a straight
  line unless it is forced to change that state by
  forces acting on it

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Newtons Second Law of Motion (Vector Form)
The vector sum (resultant) of all the forces
acting on an object equals the objects mass
times its acceleration
SF ma The acceleration a
has the same direction as the resultant force
SF.
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Newtons Second Law of Motion (Vector Form)
The vector sum (resultant) of all the forces
acting on an object equals the objects mass
times its acceleration
SF ma The acceleration a
has the same direction as the resultant force
SF.
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Forces are the origin of motion
Acceleration a F/m

• Forces

Velocity v v0 at
Position x x0 v0t ½ at2
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y
x positive y positive
x
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y
x negative y positive
x
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y
x
x negative y negative
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y
x
x positive y negative
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y
x positive y positive
x
??????
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Drawing a FBD of forces on an object (on, not
by) 1. Choose the object to analyze. Draw it as
a dot. 2. What forces physically touch this
object? This object, not some other 3. What
action at a distance forces act on the
object? Gravity is the only one for this
PHYS2053 4. Draw these forces as arrows with
tails at the dot (object). 5. Forces only! No
accelerations, velocities, Get components of
Newtons 2nd Law Choose a convenient xy
coordinate system Find the x and y components of
each force in the FBD Add the x and y components
separately
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In a rescue, the 70.0  police officer is
suspended by two cables, as shown in the figure
below Find the tension in the cables.
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y
T2 sin480
T2
T1
T1 sin350
48o
35o
x
T2 cos480
T1 cos350
w