₦airaland Forum

slow but steady the tortoise won the race.

DCDCC@ McHenry99

luckidoc:
someone help me answer this question with working

a shooter wants to fire a bullet in such a way that its horizontal range will equal 3times its maximum height. at what angle should he fire the bullet ?

H= U"2 (SIN TITA)"2/2g
R= U"2SIN 2 TITA /2g

If R=3H

then U"2SIN 2 TITA /g = 3 (U"2 (SIN TITA)"2/2g)

u"2 cancel u"2 and g cancel g


so we are left with

sin 2 tita= 3 (sin tita)"2 /2

cross multiply

recall sin 2tita= 2sin tita cos tita
hence

2sin tita cos tita= 3 sin tita x sin tita /2

sin tita cancel sin tita.

we are left with

2 cos tita = 3 sin tita/2


you know sin tita/ cos tita = tan tita.

divide both sides by cos tita


2cos tita/cos tita = [3 sin tita/ 2 ]/cos tita

2= 3tan tita/2

tan tita= 4/3

tita= tan"-1 (4/3)


tita= tan "-1 (1.333)



tita= 53.1°



THE ANGLE IS 53.1°

SuperNover:
help me out anyone in the house.

if f(y-4)=y²+2y+3, then find f(2)

51.

f(y-4)= f(2)
y= 6.
substitute Y= 6 in the equation.

McHenry99:
translation motion is the movement of the whole body...rotation motion is the circular motion of a body at a fixed point.

yes.
the fixed point is the center of the body.
it is rotational.

@ McHenry99
i think motion about the center of a body is rotational while translational motion is the motion about the edges of the body.

McHenry99:
The half life of a radioactive element is 9days. What fraction of the atoms has decayed in 36days
a. 1/16 b. 1/4 c. 1/32 d. 15/16


An electric kettle with negligible heat is rated at 2000watts. if 2kg of water is put in it how long will it take the temperature to rise from 20° to 100°c [specific heat capacity =4200Kg/K]
a. 336s b. 420s c. 168s d. 84s


A convex lens of focal length 10cm is used to form a real image which is half the size of the object. How far from the object is the image?
a. 45cm b. 30cm c. 15cm d. 20cm


When a ball rolls on a smooth level ground, the motion of its centre is
a. translational b. random c. oscillatory d. rotational



Good morning guys.

AAAD

McHenry99:
When a yellow card is observed through a blue glass, the card would appear as a. black b. green c. red d. white e. Purple


The product PV Where P is pressure and V is volumes has. the same unit as
a. Force b. power c. energy d. acceleration e. none of the above.


A household refrigerator is rated 200Watts. if electricity costs 5K per KWh what is the cost of operating it for 20days?
a. N4.80 B. N48.00 C. N480.00 D. N4800.00 E. N240.00

ACC

McHenry99:
What is the number of hydrogen ions present in a solution containing 4.9g of tetraoxosulphate (vi) acid (H=1 S=32 O=16)

mole of H2SO4= 4.9/98= 0.05mole

mole of H+= 2x 0.05

= 0.10mole

number of ions= 6.02*10"23 * 0.1

=6.02*10"22 ions.

SwagkingDope:
Which of these is the smallest?
A.DNA B.Chromatin C.Gene D.Chromosome

C

SwagkingDope:
What enzyme helps in the forming of bolus?
A.Pepsin
B.Renin
C.Mucin
D.Ptaylin

D

McHenry99:
An eruption pollution an environment with gas suspected to be H2S, a poisonous gas. A residue team should spray the environment with?

A. water


B. moist SO2


C. acidified KMnO4 and water


D. water, acidified KMnO4 and oxygen

hmm. B

clintonopah:
O is -2 ...explain please

O is -1 in peroxides.

clintonopah:
how please

the oxidation number of oxygen in peroxides is -1 and -1/2 in super oxides.
so, the oxidation number of hydrogen peroxide would be
2H +2O= 0

2H= -2(-1)

2H= 2

H= 1



and the oxidatoon number of hydrogen in all hydride is -1.

clintonopah:
dc

NO bro.

@RobinHez
liver.

1 the oxidation number of hydrogen in H202 is? a. 1 b -1 c -2 d +2 2. the oxidation number of hydrogen in PH3 is? a. -5/3 b. -1 c +1 d 1/3

McHenry99:
Gunpowder is made from charcoal, sulphur and potassium trioxonitrate (V). The salt in the mixture performs the function of?

A. an oxidant
B. a reductant
C. a solvent
D. a catalyst

View Explanation
Question No:1252
Which of the following reactions is (are) feasible?
(i)Br2(I) + 2Cl(aq) 2Br(aq) + Cl2(g)
(ii) 2l(aq) + Br2(I) 2Br(aq) + I2(s)
(iii) 2F(aq) + Cl2(g) 2Cl(aq) + F2(g)
(iv)2F(aq) + Br2(I) 2Br(aq) + F2(g).

A. i
B. ii
C. i and iii
D. iii and iv

View Explanation
Question No:1253
Bleaching powder, CaOCl2.H2O, deteriorates on exposure to air because?

A. it loses its water of crystallization
B. atomspheric nitrogen displaces chlorine from it
C. carbon (IV) oxide of the atmosphere displaces chlorine from it
D. bleaching agents should be stored in solution

View Explanation
Question No:1254
The products of the thermal decomposition of ammonium trioxonitrate (V) are?

A. N2O and oxygen
B. NH3 and oxygen
C. nitrogen and water
D. N2O and water

View Explanation
Question No:1255
The scale of a chemical balance is made of iron plate and coated with copper electrolytically because?

A. iron is less susceptible to corrosion than copper
B. copper is twice as susceptible to corrosion as iron
C. copper is less susceptible to corrosion than iron
D. copper and iron are equally susceptible to corosion

CBCCC

McHenry99:
The four classes of hydrocarbons are?

A. ethane, ethene, ethyne and benzene


B. alkanes, alkenes alkynes and aromatics


C. alkanes, alkenes, alkynes and benzene


D. methane, ethane , propane and butane



View Explanation

Question No:1232

Which of the following compounds has the highest boiling point?

A. CH3CH2CH2CH2HO


B. CH3CH2CH2CHO


C. CH3CH2CH2CH3


D. CH3CH2OCH2CH3



View Explanation

Question No:1233

Detergents have the general formula?

A. R(CH2)nOH


B. RSO3-Na+


C. RSO-2Na+


D. RSO2H



View Explanation

Question No:1234

What process would ammoniacal liquor and coke?

A. Steam distillation


B. Destructive distillation


C. Liquefaction


D. Hydrolysis



View Explanation

Question No:1235

The formula of a compound formed in a reaction between a trivalent metal M and a tetravalent non-metal X is~?

A. MX


B. M3X4


C. M4X3


D. M3X2

The forces holding naphthalene crystals together can be overcome when naphthalene is heated to a temperature of 354K resulting in the crystal to melting. These forces are known as?

A. coulombic


B. ionic


C. covalent


D. Van der waals

BABBCD