MiniDrillHomework 1

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Mini-Drill/Homework (1)
y
x
A mass m block slides down a frictionless
incline. If the block started from rest at height
yi, determine the final speed of the block when
it reaches the bottom of the incline.
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Mini-Drill (1) Solution
y
x
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Mini-Drill (1) Solution
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Mini-Drill/Homework (2)

• Problem 37, page 149 A morsel of food with a
  mass of 4.2 g is injected into the esophagus with
  an initial speed of 2.5 cm/s. On the way down to
  the stomach, the walls of the esophagus exert an
  upward resistive force of 2.7 10-3 N on the
  morsel. If the esophagus is 20.0 cm long, with
  what speed does the morsel of food enter the
  stomach?

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Solution
y
x
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Mini-Drill/Homework (3)

• A block starts from rest at a height of 5.0 m and
  slides down a frictionless incline. When the
  block reaches the ground, it slides on a rough
  surface with a coefficient of Kinetic friction mk
  0.23. How far does the block slide before it
  comes to a stop?

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Conservation of Energy
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Mini-Drill/Homework (4)

• Problem 63 (b), page 150 Two objects are
  connected by a light spring passing over a light,
  frictionless pulley. The 5.00 kg object is
  released from rest at a point 4.00 m above the
  floor. Determine the speed of each object at the
  moment the 5.00 kg object hits the floor.

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Solution
See lecture notes on how the final speed equation
was derived.
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Homework

• Problem 43, page 149 Starting from rest, a 10.0
  kg block slides 3.00 m down a frictionless ramp
  (inclined at 30.0o from the floor) to the bottom.
  The block then slides an additional 5.00 m along
  the floor before coming to a stop. Determine (a)
  the speed of the block at the bottom of the ramp,
  (b) the coefficient of kinetic friction between
  the block and floor, and (c) the mechanical
  energy lost due to friction.

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Solution (a)
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Solution (b)
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Solution (c)
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Extra Homework

• Problem 64, page 150 Two blocks, A and B (with
  mass 50 kg and 100 kg, respectively), are
  connected by a string. The pulley is frictionless
  and of negligible mass. The coefficient of
  kinetic friction between block A and the incline
  is mk 0.25. Determine the change in the kinetic
  energy of block A as it moves from C to D, a
  distance of 20 m up the incline if the system
  starts from rest.

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Solution (prob 64)
A
B
D
C
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Solution (prob 64)
y
x
B
A
D
C
Where n mg cosa
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Solution Prob 64
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Solution (prob 64)
A
B
D
C
Conditions for the problem
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Solution Prob 64
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Solution Prob 64
You can also get this answer using Newtons Laws
of Motion.