₦airaland Forum

Eben331:
(1) If 21g of alcohol of density 0.7g/cm^3 is mixed with 10g of water, what would be the density of the resulting mixture? (a) 780g/cm^3 (b) 0.78g/cm^3 (c) 30g/cm^3 (d) 10g/cm^3 (2) For a particle having an x coordinate varies in time according to the expression x=4t-2t^2, the instantaneous velocity of the particle at t=2.5secs is (a) 12m/s (b) 6m/s (c) 0m/s (d) 10m/s PLS SHOW UR WORKINGS!!

Mass of Alcohol -- 21g
Density -- 0.7g/cm^3

Volume -- Mass/Density

-- 21/0.7
-- 30cm^3

Mass of Water -- 10g
Density -- 1g/cm^3

Volume--Mass/Density

-- 10cm^3

Density of the mixture -- Total mass of the mixture/Total volume of the mixture

21+10/30 + 10

-- 0.775g/cm^3
--- 0.78g/cm^3

2. B

Adolak:
This is wrong. The question is to find mass. Not mass conc.
Then you used the H conc instead of OH concentration as it is NaOH.

I got 0.0202g though. Don't know if I'm correct

Holee shit. . Thanks man, totally skipped my mind.

freshsteph:
A hose lying on the ground shoots a stream of water upward at an angle of 40' to the horizontal. The speed of the water is 20m/s as it leaves the hose. How high up will it strike a wall which is 8.0m away
A. 2m high
B. 5.4m high
C. 4m high
D. 6m high




H=maximum height reached...



H=u^2sin^2@/2g



H=20^2×sin^2 40/20


H=8.42m


R=horizontal range=8m


sin40=x/8.42


x=sin40×8.42


x=5.41m

This one is correct, but I still can't wrap my head around how you got it..

Can you please amplify?

freshsteph:
1. A cord passing over a frictionless massless pulley has a 4kg object to one end and a 12kg object fixed to the other end. Find the acceleration and the tension in the end.
A. 4.9m/s^2, 59N
B. 6.0m/s^2, 57N
C. 2.5m/s^2, 59N
D. 9.0m/s^2, 60N
Take g as 9.81m/s^2




applying Newton's second law.




4g-T=4a


T=12a


4g-12a=4a


4g=16a



a=4g/16


a=2.5m/s^2




Tension in which end bro

This is wrong.

Physics

1. A cord passing over a frictionless massless pulley has a 4kg object to one end and a 12kg object fixed to the other end. Find the acceleration and the tension in the end.
A. 4.9m/s^2, 59N
B. 6.0m/s^2, 57N
C. 2.5m/s^2, 59N
D. 9.0m/s^2, 60N
Take g as 9.81m/s^2

2. A hose lying on the ground shoots a stream of water upward at an angle of 40' to the horizontal. The speed of the water is 20m/s as it leaves the hose. How high up will it strike a wall which is 8.0m away

A. 2m high
B. 5.4m high
C. 4m high
D. 6m high

3. The ratio of linear expansivity of copper to iron is approximately 1.5. A specimen of iron and a specimen of copper expand by the same amount per unit rise in temperature. The ratio of their lengths is
A. 3
B. 1.5
C. 1.32
D. 1
E. 0.67

4. A solid object weighs 24g in air, 16g in water and 20g in oil. The ratio of the density of the solid to that of oil is??

Show your workings..

Eben331:
Someone should pls solve this questions.

NaOH + H20 ----- Na+ + OH-

Find the hydrogen ion concentration

Ph = -log(H+)

10.5 = -(logH+)

H+ = Antilog -10.5

= Antilog -11 x Antilog +0.5
= 1 x 10^ -11 x 3.1622
= 3.16 x 10^-11 M

Volume = 0.8dm^-3

Therefore, mass conc = molar mass x molar conc

x/0.8 = 40 x 3.16 x 10^ -11

x = 1.0112 x 10^-9g

Orezy5, how correct is this?

freshsteph:
Bring it in Teflon blixx

Bring what on??

Questions?

Eben331:
You are highly welcome. Which department are you??

Mind posting Physics Utme based questions?? I'm quite rusty with physics

A string is put under a tension of 50N. A transverse wave setup in the string can be represented by y=0.25sin(2.28x-966t), where x is in meters and t is in seconds. Calculate the mass per unit length of the string?

DrBESTJC:
Quick Revision In CHEMISTRY

Solubility of salts in water.

Solubility Rules

1) All salts of sodium,Potassium and ammonium are soluble in water.
2) All trioxonitrate (V) salts are soluble in water.
3) All chlorides are soluble in water; except those of Lead, mercury and silver that are insoluble in water.
4) All tetraoxosulphate(VI) salts, are soluble in water ; except those of lead and barium. Calcium tetraoxosulphate (VI), CaSO ₄ is only slightly soluble in water.

5) All trioxosulphate (IV) salts are insoluble in water;except those of sodium,Potassium and ammonium that are soluble.

6) All trioxocarbonate (IV) salts are insoluble in water; except those of sodium,Potassium and ammonium that are water-soluble.

7) All sulphides, S^2- are insoluble in water; except those of sodium,Potassium and ammonium that are soluble.

8 ) All acid salts are soluble in water.

Note:
1) Gases, such as ammonia,NH₃ and Hydrogen Chloride, HCL are highly soluble in cold water. Infact, they react with water.Their aqueous solutions are therefore used as laboratory reagents.

2) Gases such as SO₂ , NO₂ , CL ₂ , H₂ S , N₂O and CO₂ are fairly soluble in water; hence, they are not collected over cold water during their laboratory preparations. H₂S is collected over warm water.

3) Other gases such as O₂ , N₂ , H₂ and CO are only slightly soluble in water;they can be collected over water.

Understanding Chemistry..

Me likey.

Eben331:
A hydrometer has a weighted bulb of volume 30cm^3 and a uniform stem with a cross-sectional area of 1cm^2. When floating in water 3cm of the stem is immersed. What length of this stem will be immersed when the hydrometer floats in a liquid of density 0.89gcm^-3. PLS SHOW FULL WORKINGS! CC: DrBESTJC, TeflonBlixx and others.

Density is inversely proportional to height. .

Density of water x height in water = Density of liquid x height in liquid..

Where density of water is 1gcm^3
Height in water is 3cm
Density of liquid is 0.89gcm^3
Height in liquid is unknown

3 x 1 = 0.89 x h

3 = 0.89h

3/0.89 = h

h =3.37cm

DrBESTJC:
Please Maths gurus here:
How can you solve for the squareroot of 2 or 13 or 2225 without calculator?

Here.

Aceed:
A ball of mass 10kg strikes a wall normally with a velocity of 5ms-1 and travels back with
the same velocity. Calculate its impulse on the wall.


Calculate the velocity of the wave represented by the following wave equation
y =20sin(60(pie)x - 0.5(pie)x) ,
if all the distances are in metres.

A stone is projected vertically upwards with a velocity of 20ms. Two seconds later, a second stone is projected similarly with the same velocity. When the two stones meet, the second one is rising at a velocity of 10ms. Calculate (i)the length of time the second stone is in motion before they met. (ii) velocity of the first stone when they met. (g=10ms)




PS I NEED WORKINGS. DON'T JUST COME AND DROP ANSWER


CC EBEN331, DAMAYOGENIUS18, TEFLONBLIXX

Typing stuffs is stressful, really. .

Do you mind if I snapped the solutions?

Eben331:
3(ii) time=50s and 150s You are required to use 37.5km as your height and not 50km.

I'm sorry, I'm not understanding..

Initial horizontal Velocity= 1, 000m/s. .
Initial vertical velocity = 0..

V^2 = U^2 + 2gh.. .Since a projectile has no initial component in the vertical direction.. U =0. . Vx=Vy= 1000m/s..

1000^2 = 2 x 10 x h

1 x 10^6 = 20h..

h = 50km

b. The time taken

V = U - gt

0 = 1000 - 10t
t = 100s..

c. Instantaneous velocity is velocity at any instant. . U is 0..

V = gt
V = 10 * 20
V = 200m/s

V = gt
V = 10 * 50
V = 500m/s

Aceed:
A man can row a boat at 4kmhr in still water. He rows the boat about 2km upstream and 2km back to his starting place in 2hrs. How fast is the stream flowing?


A plane is headed north with a velocity of 400kmhr and a westwind is blowing at 70kmhr. Find the distance of the plane from its base in 2 hours.


An antiaircraft shell is fired vertically upward with a muzzle velocity of 1000ms. Calculate the (i) instantaneous velocities at the end of 20secs and 50 secs (ii) When will its height be 37.5km? Inteprete your result. Neglect air resistance




cc TeflonBlixx, Damayogenius18

Since the stream is flowing, the total velocity of the boat in the flowing stream is equal to the velocity of the boat in still water and the flowing stream

Let the flowing stream be yKm/hr

When rowing upstream, the boat moves at (4 - y)km/hr. .

When rowing downstream, the boat moves at (4 + s)km/hr. .

A.V = Displacement/time. .

Make time the subject of the formular. .

The time taken to row 2km upstream
= 2/4 - s

The time taken to row downstream
= 2/4+s

The total time taken = 2hours

2/4 - s + 2/4 + s = 2 hours..

Multiply all through by 1/2. .

1/4 - s + 1/4 + s = 1. .

Multiply through by (4 - s)(4 + s) to eliminate the denominator. .

8 = 16 - s^2

S^2 =16 - 8

S^2 = 8..

S = 2.828km/hr..


2. The second one, apply the parallelogram law of velocities. . The angle is inclined at 90 degree to each other. . Find the resultant velocity

R^2 = 400^2 + 70^2
R^2 = 160, 000 + 4900
R^2 = 164900
R= the square root of 164, 900
= 406.07Km/hr. .

Therefore,

Distance = Resultant Velocity x time. .

406.07 * 2
= 812.14km..

Typing is strenuous.. Bleep!

Aceed:
Na so I see am for answer booklet but how una take dey get am na im I wan know

H = I^2RT

Since the resistors are in parallel, find the resistance. . 1/R =1/40 + 1/40. . When you get the R, then convert 5minutes into seconds. . Then you solve.

E= 1.2 * 1.2 * 20 * 300

= 8640J or 8.64KJ

Great!!

The chasm that exists amongst the medical and health science students should be gotten rid of. It is of no practical use filling students with dumb stories of how they are better than others. Talk about misplaced priorities.

Aceed:
abeg work am for me


A stone of mass 5g is projected with a rubber catapult. If the catapult is stretched through a distance of 7cm by an average force of 70N, calculate the instantaneous velocity of the stone when released.


An elastic string of l is stretched through a length e by a force F. The area of cross-section of the string is A and its Young modulus is E. Deduce the expression between F, E, e and l.


A spiral spring loaded with a piece of metal, extends by 10.5cm in air. When the metal is fully submerged in water, the spring extends by 6.8cm. Calculate the relative density of the metal (Assume Hooke's law is obeyed)




cc Damayogenius18, TeflonBlixx


P.S: I NEED WORKINGS AND EXPLANATIONS. DON'T TELL ME TO USE DO IT LIKE THIS OR LIKE THAT, I NEED WORKINGS!!!

1. F = ma

70N = 0.005a

a= 14, 000m/s^2

To get the instantaneous velocity. . Since it is released from rest, u = 0
V^2 = U^2 + 2as

Where V is unknown, U is zero, a is 14, 000 and S is the distance the catapult was pulled through which is 0.07m

V^2 = 2 x 14, 000 x 0.07

V^2 = 1960

Take root of both sides,

V = 44.27m/s

2. There is nothing to explain here tbh. . Young Modulus, Make F the subject of the formular lobatan.. You can get more info from your textbook btw..

3. This is a mixture of Hooke's and Relative density

R.D = Length in air
-------------------
Upthrust in water

Upthrust in water = Length in air - Apparent length on the spring balance

= 10.5 - 6.8
= 3.7

Therefore, 10.5
-------
3.7
= 2.837


The first one. .

Using extrapolation. .

64.992 - 63.000 = x
------------------------- ----
75 - 63 100

Subtract and cross multiply. .
12x = 199.2

Divide both sides by 12

x = 16.6 degree celsius. .

Aceed:
1. The electric resistance of the element in a platinum resistance thermometer at 100c, 0c and room temperature are 75.000, 63.000 ang 64.992 ohms respectively. Use these data to determine the room temperature.

2. Find the electrical energy expended by an electric lamp labelled 100W in 8 seconds.


cc damayogenius

Use extrapolation method for the first one

Power x time for the second one

dprpikin:
This question is one that involves a bad thermometer. What we are doing basically, is to compare the reading of the bad thermometer with what a good thermometer would have read. And in doing so we need to know the accurate boiling point at 700mmHg.

Since steam obeys the ideal gas laws, we can now use the ideal gas equations. To apply this equation we need another set of boiling point and pressure. That is what led to quoting the boiling point of water (100°C), at standard atmospheric pressure (760mmHg).

We are not concerned with the melting point, as pressure does not affect the melting point of ice. And of course, ice does not obey the ideal gas laws.

Regelation?

Manyoo fans right now. .

But but we won the transfer window. .

dopeJemi:
That's a fat lie, Person wey give ball away more than 4 times for first half? Had two to three chances to equalize? Him crosses na either direct to keeper or e no pass una first defender? Na that one na do well? Rashford is a fncking bastard and no be today I know

Don't cry me a river babee

Cry me a lagoon. .

We are here again, We are again. .

Father we are here again. .

Holy ghost fire take control

Xsem:
Are you for real? The result is awesome.

Why am I seeing a lot of 'Fs'

Mehn. . You must have another definition of 'beautiful'

Damayogenius18:
Day 6 reading group..M sori..won't be able to post tonight class on nairaland...I av posted it on what's app..for those that are member who are not on what's app..I will try to post it to ur email b4 midnight...it's time consuming posting here on nairaland and it may inconvenient others who don't want to be part of the group...

Add me up. . 08024110113

DrBESTJC:
CHEMISTRY.

1 : Calculate the pH of 0.2 mol dm^-3 of Ca(OH)2, assuming that Ca(OH)2 is a strong electrolyte.
(A) 10.6
(B) 12.5
(C) 5.1
(D) 8.0

2 : The concentration of H3O+(oxonium) ions in 1.0 mol dm^-3 solution of C6H5COOH(benzoic acid) is 8.0 * 10^-3 mole per dm^3.Calculate its percentage ionization......
(A) 0.545%
(B) 0.888%
(C) 0.213%
(D) 0.725%

Number 1 has a little glitch. . The Molar concentration should be 2 x 10^-4 instead. . Can't type much. .

Number 2 is the the concentration of H+ ions multiply by 100 divided by the molar concentration of the solution which will give 0.8%

I was here. .

Eben331:
A...As the temperature increases, the rate of reaction increases.

For every 10 degree increase in temperature, the rate of reaction doubles. . B

Nltaliban:
Your number.. I'll add you manually

Thanks

Nltaliban:
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You need a group with matured brains that are never tired of learning?.
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Cc
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The link isn't functioning. . .