The graphs of the following equations are drawn:
1. y = 3x - 2
2. y = x^2
3. y = 1 - x^2
4. y = x + 6
3 and 4
An ore of lead contains 70 % of PbS.
Calculate the mass of lead that can be extracted from 478k o
...
The graphs of the following equations are drawn:
1. y = 3x - 2
2. y = x^2
3. y = 1 - x^2
4. y = x + 6
3 and 4
An ore of lead contains 70 % of PbS.
Calculate the mass of lead that can be extracted from 478k of the ore. (Ar: Pb = 207; S = 32)
A - 28.98kg
B - 41.4 kg
C - 144.9 kg
D - 289.8 kg
E - 414.00kg
Answer:
478 x 0.7 = 334.6 mass of PbS
334.6 / (207+32) = 1.4 = no. of moles of PbS
1.4 x 207 = 289.8 kg = mass of lead
Therefore D is the answer.
The energy in joules (E) associated with a photon of radiation is related to its frequency in hertz (f) by the equation: f = E / h where h is a constant (6.63 x 10^-34). What is the energy of a photon of radiation if 5 waves of this radiation are produced in 1 x 10^-13 seconds?
A 1.33 x 10^-21J
B - 6.63 x 10^-21 J
C - 3.32 x 10^-20 J
D - 1.51 x 10 ^46 J
E - 7.54 x 10^46 J
Calculate the frequency:
Frequency = 1 / period.
The period is the time taken for one wave to take place.
If 5 waves take place in 1 x 10^-13 seconds, then 1 wave would take place in (1 x 10^-13) / 5 seconds = 2 x 10^-14 seconds.
So the frequency = 1 / 2 x 10^-14 = 0.5 x 10^14 = 5 x 10^13.
E = 5 x 10^13 x 6.63 x 10^-34 = 3 something ^- something. The best answer choice would therefore be C.
The book says:
F = no. of vibrations / time
so f = 5 / 1 x 10^-13
tip
Check workds like must of may very carefully.
These are often, but not always, shown in bold type.
The sum of the roots of a quadratic equation is 7, the product of the roots is 9. What is the equation?
x^2 - 7x + 9 = 0
The roots are the solutions of the equation. We don't know what the roots are, so we call them a and b. SO when we factorise the quadratic equation it looks like:
(x - a)(x - b) = 0
Multiplying out the brackets:
x^2 - ax - bx + ab = 0
x^2 - (a +b)x + ab = 0
From the question we know that:
a + b = 7
ab = 9
and substituting these into the quadratic equation:
x^2 - 7x + 9 =0
What is the symbol for a diode?
what is an integer? and give some examples.
A whole number. 1, -1, 0.
w < x^2, x > y^2, y^2 < z^2 and x > z
Which of the following must be true?
A - w < x
B - w > y
C - w < z
D x > y
E y < z
D cos it's an INTEGER!!!
A bullet of mass 50 g is fired from a rifle with a velocity of 300 m/s. It hits a bank of earth and after travelling 60cm into the bank comes to rest.
What is the average stopping force of the earth in the bank on the bullet?
Force = change in momentum / time taken.
Initial momentum = 50 x 300 / 1000 = 15 kgm/s
Therefore change in momentum = 15kgm/s
Use SUVAT to calculate time taken.
s = (u+v)/2 x t
so 0.6 m = 150m/s x t
therefore t = 0.6 m / 150 m/s = 4 x 10^-3
So: Force = 15 kgm/s divided by 4 x 10^-3 = 3.75 x 10^3 N.
Which graph correctly shows how the resistance (R) varies with applied voltage (V) for a resistor at constant temperature?
It would be one with a straight line because...
The resistance of a resistor is constant - only current would change.
Resistance only changes slightly with temperature.
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