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Unformatted text preview: DISCUSSION PROBLEM 1.1: ... answers ... • Variation of length with temperature?
Origin of standardized units:
LENGTH • Do you measure to the lefthand edge of the
scratch, or the middle or the righthand edge? • A “fallback” unit of length ... a bar of platinum iridium with two scratches, exactly 1 meter apart.
DISCUSSION PROBLEM 1.1:
Can you think of reasons why this may not be such a
good standard today? 1 DISCUSSION PROBLEM 1.2: ... answers ...
Ordinary numbers. π= circumference [L]
=
⇒ dimensionless.
diameter
[L ] θ= arc length [L]
=
⇒ dimensionless.
radius
[L ] DISCUSSION PROBLEM 1.2:
Can you think of any physical quantities that do not have
dimension? Note that although θ has no dimension, it does have a
unit (radians, degrees)! Specific gravity = weight of an object
weight of an equal amount of water ⇒ dimensionless. 2 DISCUSSION PROBLEM 1.3:
Population ... answer ... ≈ 300,000,000 Average family ≈ 5 people 1 cup = 8oz
In each of 60,000,000 families: DISCUSSION PROBLEM 1.3:
Estimate how many quarts of milk (all kinds) are
consumed each day at breakfast in the U.S. (a) Four have cereal, or equivalent,
1 cup each = 4 × 1 = 2 cup.
2
2
(b) Two have 2 cups of coffee/tea with milk
1 th cup each = 2 × 2 × 1 = 1 cup.
8
8
2
(c) One drinks milk, = 1 cup.
Total consumed by each family
≈ 3 12 cups ≈ 26 oz
∴ Total consumed at breakfast:
26 × 60, 000, 000
=
≈ 50 million quarts!
32
How many cows required? 3 CLASS PROBLEM [1.2]: ... answer B. CLASS PROBLEM [1.2]:
Price of gold: 1 ounce of gold ⇒ $1000. What’s the minimum number of men you think would be
required to carry a box containing 1M$ worth of gold a
distance of 30m?
A: ~ 1 man
B: ~ 2 men
C: ~ 5 men
D: ~ 10 men
E: more than 10 men Therefore, weight of 1M$ of gold is:
1, 000, 000
= 1000 ounces.
1000
But 16 oz ⇒ 1 pound.
∴ 1M$ weighs : 1000
≈ 63 pounds.
16 Assume each man can carry ~ 30 → 40 pounds ...
... then it will require ~ 2 men! 4 ...
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 Spring '08
 Guzman
 Physics

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