Q2. Richard is making glass fibre. He starts with a with a diameter of 5cm and height of 8cm. He spins this into glass fibre with a circular cross section of 0.1cm. What length of the glass fibre does he make? Give your answer correct to the nearest metre.
Q3. A firm that sells cat food wants to change the size of its tins. The tin has a diameter of 6cm and height of 12cm
a)What is the volume of this tin correct to 1dp?
b)The new tin must have the same volume. The new diameter is 8cm. What is the height of the new tin? Give your answer correct to the nearest millimetre.
And I would be very greatful if you show me the working out so I can learn it? Thank you all. Much love.
2007-01-09 07:06:06 · 8 answers · asked by HelloSunshine:) 2 in Science & Mathematics ➔ Mathematics
Q2) Calculate the volume of the material Richard starts with. Area of circle times the height. Then calculate the area of the finished product. divide the answer you got for the volume by this area. your answer should be 19999.19 cm, about 200metres.
Q2) a)Volume is Area of circle times the height. (22/7 X 3 squared) X 12 = 339.3
b)Divide the volume found by the new area of circle. Ans=6.7
2007-01-09 07:26:37 · answer #1 · answered by samukeliso 2 · 1⤊ 0⤋
Even though you are probably just copying this, if you actually WANT to learn it, here's an explanation.
Q2) Richard is technically starting with a cylinder of diameter 5 cm and height 8 cm. He turns this into a cylinder of the same volume, but with a 0.1 cm diameter.
To convert this you must use the formula for the volume of a cylinder which is V = Ï*r^2*h.
Plug in the variables to get: V = Ï * (2.5)^2 * 8
= 50Ï
Now, you must find the height of the other cylinder, it having the same volume.
50Ï = Ï(0.05)^2*h
50Ï = Ï(0.0025)*h
Solve for h
h = (50Ï)/(0.0025Ï)
h = 20,000 cm
h = 200 m
Q3)
a.
V = Ï*r^2*h
V = Ï*(3)^2*12
V = 108Ï
V = 339.3 cm
b.
339.3 = Ï(4)^2*h
339.3 = 16Ï*h
h = 339.3/16Ï
h = 6.75 cm
h = 675 mm
2007-01-09 15:55:35 · answer #2 · answered by smawtadanyew 2 · 0⤊ 0⤋
Q2.
Find current volume: V = Ah
A = Ï r²
(5cm/2)² * Ï
V = 8 cm * (5cm/2)² Ï
V = 10 Ïcm³
The volume does not change, but the circular cross section does. The new diameter is .1cm (I'm guessing that's what they meant...) The new area is
[(1/2)(1/10)cm]² Ï
Divide volume above by that
10Ï cm³ / Ïcm² /2²*10²
or
10*2² * 10² cm
10² cm = 1 m
that's 40 m
2007-01-09 15:21:27 · answer #3 · answered by bequalming 5 · 0⤊ 1⤋
Q2: His fiber went from a diameter of 5 cm down to 0.1 cm: a 50x decrease. Therefore, to conserve mass, the length has to experience a 50x increase (50 x 8 = 400 cm = 4 meters)
Q3:
a)Volume = surface of circle x height
surface = PI x Diameter^2 / 4
surface = 3.14159 x 6x6/4 = 28.274 cm^2
volume = 88.86 x 12 = 339.29 cm^3
b) New surface = 3.14159 x 8x8/4 = 50.26 cm^2
height = volume / surface
height = 339.29 / 50.26 = 6.75 cm
I let you adjust the precision (I don't know what is 1dp).
2007-01-09 15:19:14 · answer #4 · answered by catarthur 6 · 0⤊ 1⤋
Q2
V = 3.14 x 2.5² x 8cm³ = 157cm³
You now say cross section is 1cm.
I am going to assume that you mean the circular cross sectional area is 1cm² i.e. A =1cm²
157 = A x h = 1 x h
h = 157cm = 1.57m = 2m (to nearest metre)
Q3
a) V = 3.14 x 3² x 12cm³ = 339.1cm³
b) 339.1 = 3.14 x 4² x h
339.1/(3.14 x 16) = h
h = 6.75cm = 67.5mm =68mm to nearest mm
2007-01-09 18:00:49 · answer #5 · answered by Como 7 · 0⤊ 0⤋
bequalming has the wrong answer although the theory is right, there's a mistake in the calculations.
samukeliso's got it right.
2007-01-09 15:37:11 · answer #6 · answered by Anonymous · 0⤊ 0⤋
hahahahahaha please show working so you can learn it. thats a good one. because of course you would never dream of copying it straight down onto your paper. hahahahaha.
pay more attention at school
2007-01-09 15:17:13 · answer #7 · answered by big ric 2 · 0⤊ 0⤋
Sorry i was never that good at maths!
2007-01-09 15:10:55 · answer #8 · answered by lisaweider 3 · 0⤊ 0⤋