Homework 131

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course Mth 271

10/19/2010

If your solution to stated problem does not match the given solution, you should self-critique per instructions at

http://vhcc2.vhcc.edu/dsmith/geninfo/labrynth_created_fall_05/levl1_22/levl2_81/file3_259.htm

.

Your solution, attempt at solution.

If you are unable to attempt a solution, give a phrase-by-phrase interpretation of the problem along with a statement of what you do or do not

understand about it. This response should be given, based on the work you did in completing the assignment, before you look at the given solution.

013. `query 13

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Question: `q query problem 2.3.37 . Which graph matches the graph of the bus and why?

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Your solution:

Graph 2

confidence rating #$&*: 3

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Given Solution:

** The bus only makes periodic stops, whereas the graph for III only comes to a stop once. I would matche the bus with II. **

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Question: `q describe the graph of the car with no traffic and no lights

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Your solution:

I would say graph 1 because that graph has a continuous line which would make since because the car in not stop by any traffic lights or traffic.

confidence rating #$&*: 3

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Given Solution:

** The car matches up with (I), which is a continuous, straight horizontal line representing the constant velocity of a car with no traffic and no

lights. *&*&

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Question: `q describe the graph of the car with heavy traffic

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Your solution:

I choose graph 3 because the car would have to speed up and slow down at different times because of the traffic. Graph 3 is perfect because of its

increasing and decreasing intervals.

confidence rating #$&*: 3

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Given Solution:

** The car in heavy traffic would do a lot of speeding up and slowing down at irregular intervals, which would match the graph in III with its

frequent increases and decreases. **

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Question: `q query 2.4.11 5th, 2.4.10 4th; 2.5.10 (was 2.4.8) q = f(p) (price and quantity sold)what is the meaning of f(150) = 2000?

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Your solution:

f(150) = 2000 means when the price is at 150 dollars we are expected to sell 2000 units.

confidence rating #$&*: 3

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Given Solution:

*&*& q = 2000 when p = 150, meaning that when the price is set at $150 we expect to sell 2000 units. *&*&

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Question: `q what is the meaning of f'(150) = -25?

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Your solution:

This function is the derivative f'(150) = -25, so that means when the price is set at 150 dollars we will be losing 25 units at that price increase.

confidence rating #$&*: 2

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Given Solution:

** f' is the derivative, the limiting value of `df / `dp, giving the rate at which the quantity q changes with respect to price p.

If f'(150) = -25, this means that when the price is $150 the quantity will be changing at a rate of -25 units per dollar of price increase.

Roughly speaking, a one dollar price increase would result in a loss of 25 in the number sold. **

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Question: `q query problem 2.4.23 5th; 2.4.18 4th; 2.4.7 graph of v vs. t for no parachute.

Describe your graph, including all intercepts, asymptotes, intervals of increasing behavior, behavior for large |t| and concavity, and tell why the

graph's concavity is as you indicate.

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Your solution:

Starting from the origin or 0 you can see that there is a sharp increase do to the fact that the person is falling from the sky. As the person reaches

the maximum speed which in this case would be the horizontal asymptote then you would see a slight decrease in the graph due to the air resistance.

Therefore making this graph concave downward.

confidence rating #$&*: 3

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Given Solution:

** When you fall without a parachute v will increase, most rapidly at first, then less and less rapidly as air resistance increases.

When t = 0 we presume that v = 0.

The graph of v vs. t is therefore characterized as an increasing graph beginning out at the origin, starting out nearly linear (the initial slope is

equal to the acceleration of gravity) but with a decreasing slope. The graph is therefore concave downward.

At a certain velocity the force of air resistance is equal and opposite to that of gravity and you stop accelerating; velocity will approach that

'terminal velocity' as a horizontal asymptote.

The reason for the concavity is that velocity increases less and less quickly as air resistance increases; the approach of the velocity to terminal

velocity is more and more gradual **

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Question: `q What does the t = 0 acceleration indicate?

T = 0 acceleration is the beginning point, or when you’re in the plane. It’s the point before you build up speed.

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Your solution:

confidence rating #$&*: 3

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Given Solution:

** t = 0 acceleration is acceleration under the force of gravity, before you build velocity and start encountering significant air resistance.

Acceleration is rate of velocity change, indicated by the slope of the v vs. t graph. **

STUDENT QUESTION

I understand how acceleration and vel. are related, just not the first part of solution

INSTRUCTOR RESPONSE

If it wasn't for air resistance, acceleration would be equal to that of gravity.

When you first jump out you aren't falling very fast, so there isn't much air resistance to counter the acceleration of gravity, so you accelerate

pretty much at the acceleration of gravity.

You quickly speed up, and air resistance becomes more and more significant. So your acceleration becomes less than the acceleration of gravity.

Assuming the ground is far away, this continues until air resistance is effectively equal to the force of gravity, at which point your acceleration

will be zero. You will be at terminal velocity.

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Self-critique (if necessary):

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Question: `q Query Add comments on any surprises or insights you experienced as a result of this assignment.

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&#Good work. Let me know if you have questions. &#

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