ITP%20HOMEWORK

1
ITP HOMEWORK

• Ch. 2
• Mechanical Equilibrium
• Pg. 24 (1,2,4,7,8,12,14)

2
ITP HOMEWORK

• Ch. 2
• Mechanical Equilibrium
• Pg. 24 (3,5,9,10,15,16,22,23)

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ITP HOMEWORK

• Ch. 2.1-2.4
• Mechanical Equilibrium
• Pg. 24 (1-4, 7-10, 14-16)

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1. What is the difference between force and net
force on an object.
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1. What is the difference between force and net
force on an object.

• Force is a push or a pull net force is the
  combination of all forces acting on an object.

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2. What is the net force on a box that is being
pulled to the right w/ 40 N and to the left with
30 N?
30 N
40 N
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2. What is the net force on a box that is being
pulled to the right w/ 40 N and to the left with
30 N?

• 10 N to the right

30 N
40 N
8
3. What name is given to the stretching force
that occurs in a spring or rope being pulled?

• Spring force and Tension

9
4. What two quantities are necessary to determine
a vector quantity?

• Magnitude and direction

10
7. How much tension is in a rope that holds up a
20-N bag of apples at rest?

• Since the bag is at rest, it is in mechanical
  equilibrium. Therefore, there must be 20N of
  tension force to balance the 20N of weight force
  due to gravity.
• This is referred to in the book as static
  equilibrium.

11
8. What does F 0 mean?

• The sum of all forces acting on a body are
  balanced (or net force is equal to zero)

12
9. What is the net force on an object at rest?
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9. What is the net force on an object at rest?

• Zero. All forces are balanced.

14
10. When you do pull-ups and you hang at rest,
how much of your weight is supported by each arm?
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10. When you do pull-ups and you hang at rest,
how much of your weight is supported by each arm?

• Each arm supports one-half of your weight.

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14. Can an object be moving and still be in
(mechanical) equilibrium?
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14. Can an object be moving and still be in
(mechanical) equilibrium?

• Yes. If the object moves at a constant speed in
  a straight line, then the net force on the object
  is equal to zero.
• This is referred to in the book as dynamic
  equilibrium.

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15. If you pull a crate across a factory floor at
a constant speed in a constant direction, what is
the size of the force of friction on the crate
compared with your pull if your pull force is 50
N? What is the net force? Is it in mechanical
equilibrium? If so, which type?
???? of friction force
50 N of pull force
Box is moving at a constant speed and direction
to the left.
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15. If you pull a crate across a factory floor
at a constant speed in a constant direction, what
is the size of the force of friction on the crate
compared with your pull if your pull force is 50
N? What is the net force? Is it in mechanical
equilibrium? If so, which type?

• Both the pull force and the friction force are
  equal in magnitude, but are in opposite
  directions. Thus, the net force is zero and the
  object is in dynamic equilibrium.

50 N of pull force
50 N of friction force
Box is moving at a constant speed and direction
to the left
(Dynamic equilibrium)
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16. Distinguish between static equilibrium and
dynamic equilibrium.

• An object at rest is said to be in static
  equilibrium.
• An object moving in a straight line at a constant
  speed is said to be in dynamic equilibrium.
• For each case, the net force 0, thus the forces
  acting are balanced.

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22. and 23.

• 22. B is the same as D, then C and then A.
• 23. C, then D, then A is the same as B.

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5. How does a vector quantity differ from a
scalar quantity?

• Vector quantities show magnitude and direction
  and scalar quantities show only magnitude.

23
12. What two forces compress a spring inside a
weighing scale when you weight yourself?

• Your weight (your mass accelerated by gravity)
  and the support force of the floor (pushing
  upward).