Figure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic device is shut off allowing a person to work on the electronics with less risk of shock, (a) What is the time constant? (b) How long will it take to reduce the voltage on the capacitor to 0.250% (5% of 5%) of its full value once discharge begins? (c) If the capacitor is charged to a voltage V 0 through a 100-O resistance, calculate the time it takes to rise to 0. 865V 0 (This is about two time constants.)
Figure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic device is shut off allowing a person to work on the electronics with less risk of shock, (a) What is the time constant? (b) How long will it take to reduce the voltage on the capacitor to 0.250% (5% of 5%) of its full value once discharge begins? (c) If the capacitor is charged to a voltage V 0 through a 100-O resistance, calculate the time it takes to rise to 0. 865V 0 (This is about two time constants.)
Figure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic device is shut off allowing a person to work on the electronics with less risk of shock, (a) What is the time constant? (b) How long will it take to reduce the voltage on the capacitor to 0.250% (5% of 5%) of its full value once discharge begins? (c) If the capacitor is charged to a voltage V0through a 100-O resistance, calculate the time it takes to rise to 0.865V0(This is about two time constants.)
Part 3: Symbolic Algebra
Often problems in science and engineering are done with variables only. Don't let the different letters
confuse you. Manipulate them algebraically as though they were numbers.
1. Solve 3x-7= x + 3 for x
2x-1
2. Solve-
for x
2+2
In questions 3-11 solve for the required symbol/letter
3. v2 +2a(s-80), a =
=
4. B=
Ho I
2π r
5. K = kz²
6.xm=
MAL
,d=
d
7.T, 2
=
8.F=Gm
9. mgh=mv²
10.qV = mu²
80
12. Suppose that the height in meters of a thrown ball after t seconds is given by h =6+4t-t².
Complete the square to find the highest point and the time when this happens.
13. Solve by completing the square c₁t² + cat + 3 = 0.
14. Solve for the time t in the following expression = 0 + vot+at²
A blacksmith cools a 1.60 kg chunk of iron, initially
at a temperature of 650.0° C, by trickling 30.0°C
water over it. All the water boils away, and the iron
ends up at a temperature of 120.0° C.
For related problem-solving tips and strategies, you
may want to view a Video Tutor Solution of
Changes in both temperature and phase.
Part A
How much water did the blacksmith trickle over the iron?
Express your answer with the appropriate units.
HÅ
mwater =
Value
0
?
Units
Submit
Request Answer
Steel train rails are laid in 13.0-m-long segments
placed end to end. The rails are laid on a winter
day when their temperature is -6.0° C.
Part A
How much space must be left between adjacent rails if they are just to touch on a summer day when their
temperature is 32.0°C?
Express your answer with the appropriate units.
☐
о
μΑ
?
D =
Value
Units
Submit
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Part B
If the rails are originally laid in contact, what is the stress in them on a summer day when their temperature is
32.0°C?
Express your answer in pascals. Enter positive value if the stress is tensile and negative value if the
stress is compressive.
F
A
Ο ΑΣΦ
?
Ра
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