Saturday

June 25, 2016
Total # Posts: 11,475

**Physics :)**

You're welcome!
*June 14, 2014*

**Physics**

Time (hours) = Distance (km) ÷ Speed (km/h) Divide by 24 to convert into days.
*June 14, 2014*

**Physics**

T (period) = time/rev = 20 sec/ 30 rev = 2/3 sec/rev ω(angular speed) =30 rev/20 seconds =30/20 rev / sec =30/20*2π radians / s Velocity =rω =0.008m*ω m/s
*June 14, 2014*

**math check**

5P5=5!/(5-5)!=?
*June 11, 2014*

**Physics**

Upstream=300 metres/(2-1)=300 s Downstream=300/(2+1)=100 s
*June 11, 2014*

**Math**

If you follow the rules of PEDMAS, what you wrote means: a + (b/10) = a - (0.1b^2/a) -b Please confirm if you really mean if(a+b)/10 = (a-0.1b²)/(a-b) Also, post what your answer is, and explain.
*June 11, 2014*

**PHYSICS**

For a projectile with initial velocity=vi projection angle = θ with horizontal The time of flight =2visin(θ) If time is doubled with θ unchanged, vi is doubled. From range = vi²sin(2θ)/g you can figure out the increase of the range when time (and ...
*June 11, 2014*

**PHYSICS**

There is no rule. It depends on the path. Average velocity = (final position-initial position)/Δt Average velocity = ∫c dx /Δt (line integral)
*June 11, 2014*

**physics - figure missing.**

Not sure why your answer is wrong when the question is not even complete.
*June 11, 2014*

**Physics**

Half way down is 30 m down. Assuming the GPE reference is at the bottom of the cliff, then GPE=mg(30)=27072 J KE=(1/2)mv² Equate GPE and KE.
*June 8, 2014*

**Physics**

Let fulcrum be at x cm from the 0 mark. Then 1kg*x cm = 3kg*(100-x) cm Expand and solve for x.
*June 8, 2014*

**Physics**

Power=Mg(speed)*sin(θ)/0.40 watts M=total mass (passengers, train, etc.)
*June 8, 2014*

**physics**

Ek=(1/2)mv² Ep=(1/2)(KΔx)² If spring has no mass, equate Ek and Ep to solve for Δx.
*June 8, 2014*

**college physics**

Lack of better data, assume the 1.4 cm is the difference between stretched and unstretched length. Work done = Δpotential energy = (1/2)k(Δx)² First change everything to SI units then the result will be in joules.
*June 7, 2014*

**physics**

Think of throwing an egg on a wall. Would that be elastic collision?
*June 7, 2014*

**Engg Mechanics**

Resolve forces parallel to the plane: P=(m1+m2)g cos(θ) where P=force up the plane m1,m2 = masses of the blocks Normal reactions of blocks are m1g sin(θ) and m2g sin(θ) unless blocks are piled up. (confirm with your figure)
*June 7, 2014*

**statistics**

Size of set A = |A| = 110, similarly |B|=750, |C|=250 Size of Ω, sample space, S = |A|+|B|+|C|=1110 Random selection from equi-probability sample would be P(A or B)=P(A)+P(B)=(|A|+|B|)/S
*June 7, 2014*

**physics**

Convert speed to m/s: 36 km/h = 36/3.6=10 m/s In calculating train crossing bridges, we have to remember that after the head of the train has crossed the bridge (800 m), the remainder of the train is still on the bridge. So to completely cross the bridge, the time is what is ...
*June 7, 2014*

**MATH**

I think you should spend more efforts in understanding how to solve the problems, in explaining how you solved the problems (whether correctly or not) in order to help yourself. Trying to post under a different name and posting the same question multiple times, without showing...
*June 7, 2014*

**math - kindly continue**

We are listening!
*June 7, 2014*

**math Study guide updated answers check**

See other post for comments on your answers.
*June 6, 2014*

**Math**

10 choose 3 =10C3 =10*9*8/(1*2*3)
*June 6, 2014*

**Math**

In a four digit number, a digit repeated twice means 3 of the numbers are the same. Repeated more than twice means repeated 3 times, or all four digits are the same. PINs with no digit repeated more than twice would therefore mean pins which do not have identical digits. Out ...
*June 6, 2014*

**math help**

Experimental probability =(observed frequency)/size of sample space which leads to P(red)=10/35=2/7 P(blue)=5/35=1/7 ... etc also, since these probabilities are complementary, we can conclude that P(blue or red)=P(blue)+P(red) Try to work out the numbers and post for checking ...
*June 6, 2014*

**check my work MATH**

Kindly read responses to your previous posts before reposting.
*June 6, 2014*

**math**

A is correct!
*June 6, 2014*

**math**

Please try again after reading the following. If possible, please explain the reasoning of your choice. A square must have equal sides. A rectangle may have unequal sides, but sides do not have to be unequal. A rhombus must have equal sides, and one of the angles can be ...
*June 6, 2014*

**physics**

The question is incomplete. Most of the time incomplete questions remain unanswered. If you are looking for principles of conservation of mechanical energy, the answer is yes in most cases if there is no friction and no air resistance. A small ball sliding down an incline will...
*June 6, 2014*

**math Study guide 3**

1) There are 4 colours, multiplied by 20% gives only 80%, where do the remaining 20% go? Experimental probability goes with the outcome of experiments. Think along those lines. 2) 40% is correct, as you said 40%*20=8, or working directly, 8÷20=40%. 3) Theoretical is 25...
*June 6, 2014*

**math Study guide 3**

Please explain how you got your choices.
*June 6, 2014*

**Math**

They want maximum of 8-hour days, so fill up with as many 8-hour days as possible.
*June 6, 2014*

**Math**

8*6>46 not good 8*5=40, add 6 days to make 46 hours. So maximum is 5 days.
*June 6, 2014*

**math question**

Theoretical probability (assuming a fair cube) for the number 3 is 1/6 (6 faces). The experimental probability is based on an experiment, namely 67/450. Since 67 is a prime, this is the simplest fraction.
*June 6, 2014*

**math Study guide**

1) table not shown, so cannot verify. 2) what is the probability of rolling 8 times out of 20? 3) correct. 4) expected number of outcomes = probability * number of trials So 20*15%=20*0.15=3 5) See number (4) and try again. 6) What is the experimental probability of pulling 5 ...
*June 6, 2014*

**math Study guide**

What do you think for each of the problems?
*June 6, 2014*

**Math**

Let the circle pass through, in general, three points: (x1,y1) (x2,y2) (x3,y3) and the equation is to be expressed in the form x²+y²+dx+ey+f=0 The required equation may be expressed in determinant form: [y^2+x^2, x, y, 1] [y1^2+x1^2, x1, y1, 1] [y2^2+x2^2, x2, y2, 1...
*June 6, 2014*

**Statistics**

Normal distribution table give μ+2.33σ as the 99% level. Calculate the warranty period accordingly. Tell me which brand it is that has 40 years mean life! :)
*June 6, 2014*

**probability**

You're welcome!
*June 6, 2014*

**probability**

Calculate the probability that the building is protected by NO alarm. Subtract from 1.0 gives you the probability required. P(≥1)=1-(1-80%)*(1-70%) Let P(W)=x Probability of picking two whites P(WW)=x²=0.49 x=?
*June 6, 2014*

**Statistics - correction**

Last line should read 29/111
*June 6, 2014*

**Statistics**

Assuming leading zeroes count as digits, then probability of seeing 3 distinct digits = 10*9*8/1000 = 720/1000 =18/25 Probability of at least 2 identical digits = 280/1000 =7/25 If leading zeroes are not displayed, then there are 9*9*8=648 plates with distinct digits between ...
*June 6, 2014*

**trig**

Work done =F.D =F*D*cos(θ) =<0,-3400><1000sin(8°),1000cos(8°)> =3400000cos(8°) ft-lb (gravitation units)
*June 6, 2014*

**MATH**

Use the slope equation: slope = (y2-y1)/(x2-x1)
*June 5, 2014*

**Physics**

F=<-3,-7.6> Δr = <3.6,-2> Work done F.Δr = <-3,-7.6><3.6,-2> = 4.4 J
*June 5, 2014*

**algebra**

It is almost a linear function, if the 8 becomes a 9, i.e. the y-values become -7,1,9,17,25. Otherwise the answer is no.
*June 5, 2014*

**Physic**

At the beginning, the box is in uniform rectilinear motion (URM), which means that the horizontal force is just enough to balance the frictional resistance, where Pushing force, F =Frictional resistance = μkmg = 0.3 mg With increase in coefficient of friction, the net force...
*June 5, 2014*

**Physics**

We know that the intensity of the omnidirectional source is proportional the energy rate and inversely proportional to the square of the distance (inverse square law). So 1/8² = 0.5/d² Solve for d.
*June 5, 2014*

**Physics**

The magnitude |<x,y>| of a vector given as <x,y> can be obtained by a calculation similar to Pythagoras theorem. For example, |<3,4>| = sqrt(3²+4²)=5 The direction θ with respect to the x-axis can be calculated using a calculator by: θ=...
*June 4, 2014*

**physics**

Equate energy with the heat of fusion of water. (1/2)mv²=MH m=mass of bullet(kg) H=heat of fusion (J/kg) M=mass of ice melted (kg) Make sure the heat of fusion of water is converted to J/kg for your calculations.
*June 4, 2014*

**physics**

Use ΔQ=mcΔT where Q=heat in joules m=mass in kg T=temperature in °C c=specific heat in J/(kg-°C)
*June 4, 2014*

**physics**

One MW (megawatt) is 1 million watts. One watt is 1 joule / second. If the plant efficiency is 34%, it means that 34% of the energy is converted into electricity, while (100-34)=66% is dissipated as heat. So calculate the power converted to heat, and use the conversions above ...
*June 4, 2014*

**physics**

10 cos(60°)
*June 4, 2014*

**Math**

p=P(B)=0.77 q=1-P(B)=0.23 = probability of walking n=5 (days) r=3 days taking bus Given independence of choice from day to day, and probability does not vary, then we can use the binomial distribution. To calculate the probability of taking the bus exactly r days out of n: P(n...
*June 4, 2014*

**c++**

Here's a sample pseudocode. Input initial populations, p1, p2. Input growth rates, r1,r2. Input number of years to print, n. for year=0 to n output year, p1*pow(1+r1,year), p2*pow(1+r2,year) next year If you have problems getting your code to work, post your code.
*June 4, 2014*

**Geometry - need more information**

Please complete the description of the diagram and the questions.
*June 4, 2014*

**10**

Nice problem. Let ABC be the right-triangle, right-angled at C, such that AC=12, BC=6. Let the "inscribed" square share a common right-angle at C, and meet the hypotenuse AB at D. Let E be a corner of the square on AC, and F be a corner of the square on BC. Let x ...
*June 4, 2014*

**Probability**

The outcome consists of individual answers of true/false, probability remains constant throughout, use Binomial probability. P(n,r,p)=nCr*p^r(1-p)^(n-r) n=size of sample r=(exact)number of outcomes each with probability of p At most 2 means 0,1 or 2. The answer is P(20,0,0.05...
*June 4, 2014*

**Algebra**

Here we see that x cannot be zero, so replace (1/x) by y and solve the resulting quadratic. 6y²-7y+2=0 (2y-1)(3y-2)=0 y=1/2 or y=2/3 find x from y=1/x, or x=1/y x=2, or x=3/2
*June 4, 2014*

**Algebra**

BEDMAS tells us that exponents are evaluated before division, so the equation reads (x²)/5 + x/5-6=0 Multiply by 5 to get x²+x-30=0 (x-5)(x+6)=0 So x can be readily found.
*June 3, 2014*

**physics**

Distance = total of distances =10+10=20 m. average speed = total distance / total time = (30+50)/(10+30) m/s = ?
*June 3, 2014*

**Physics I NEED HELP WITH EQUATIONS**

Assuming the block is on a horizontal surface. Vertically (y): Gravitational force = mg normal reaction, N = mg (N is reaction required to remain in equilibrium) Horizontally (x): Since block moves with constant velocity, it is in dynamic equilibrium, so for equilibrium, ...
*June 3, 2014*

**math**

Let x=interest, 4000:280 = P : x converts into the equation 4000/280 = P / x which when cross multiplied gives 4000x = 280P divide both sides by 4000 to get: x(interest) = (280/4000)P =(7/100)P or =0.07P
*June 3, 2014*

**math**

See: http://www.jiskha.com/display.cgi?id=1401846779
*June 3, 2014*

**physics**

Using the idea of resistors in series and in parallel, we conclude that: resistance is proportional to length, and inversely proportional to the area. That should be sufficient to solve the first problem.
*June 3, 2014*

**linear math**

Expand the both sides of the equal sign and compare. If both sides are identical, it is an identity, i.e. equality for all values of x. If the two sides are not identical, it is an equation, valid only for certain values of x. For example, 5(x+2)=5x+10 expand 5x+10=5x+10 both ...
*June 3, 2014*

**Geometry**

If B is mid-point, then AB=10 = 2x+5=BC or x=2.5 then AC=20=8x and not 5x. So it is not possible.
*June 3, 2014*

**Physics**

That's correct!
*June 3, 2014*

**Physics**

Power = VI, compatible units are W, V, A. 10 kW = V(20 A) NOTE: 10 kW = 10000 W
*June 3, 2014*

**Physics**

Req =1/(1/R1+1/R2+1/R3+...) So, with 3 resistors, Req =1/(1/5+1/2.5+1/10) =...
*June 3, 2014*

**Physics**

Do you mean one 10Ω is in series with two 10Ω in parallel? the ones in parallel are worth 5Ω so the total equivalent resistance is 10+5=15. Use V=IR
*June 3, 2014*

**MATH**

Equation of line? y=(3/2)x+3
*June 3, 2014*

**Physics**

Correct!
*June 3, 2014*

**Physics**

The equivalent resistance, R =1/(1/10+1/20)=1/(3/20)=20/3 Ω Use V=IR to find the current.
*June 3, 2014*

**Geometry**

The area of parallelogram is Area=a*b*sin(θ) where a, b are adjacent side lengths, and θ is the included angle.
*June 3, 2014*

**Geometry**

Sorry. In that case, we make use of the fact that rhombuses have diagonals which intersect at right-angles. Thus each side is the hypotenuse of a right triangle with legs equal to the half-diagonals. Thus if s=length of each side of the rhombus, then s²=(AC/2)²+(BD/2...
*June 3, 2014*

**Geometry**

A quadrilateral with all four sides equal is a rhombus, whose area is half the product of the diagonals AC and BD.
*June 3, 2014*

**physics**

weight = 11.2 N = mg => m=11.2/9.8 = 1.143 kg new weight = 13.1 = m(g+a) a=13.1/1.143-9.8=1.661 m/s²
*June 3, 2014*

**math -logarithm**

729=9³ log9729 = 3 25 = (1/5)-2 log(1/5)25 = -2 for a=bc² rearrange to (a/b) = c² and proceed similar to above.
*June 3, 2014*

**math -logarithm**

x=log1010000 10x=10000 therefore x=4, or log1010000=4
*June 3, 2014*

**Math - Data Management**

Binomial distribution gives us 5C2*(.5)²(.5)³ =10(.5)^5 =0.3125 E(x)=2400*0.3125=750
*June 3, 2014*

**physics**

vf=vi+at a=-0.08 m/s² vi=1 m/s t=4 s
*June 3, 2014*

**physics - insufficient information**

Graph is a necessary ingredient of this question.
*June 3, 2014*

**physics**

Δx = vi*Δt+(1/2)aΔt² vi=0 so Δx = (1/2)aΔt² a=2Δx/Δt² =2*420/(32²) =(105/128) m/s² vf=aΔt =(105/128)*32 =26.25 m/s (not extremely fast for a plane)
*June 3, 2014*

**Physics :)**

You're welcome!
*June 3, 2014*

**Physics**

Correct.
*June 3, 2014*

**physics**

Her resultant speed is perpendicular to the flow of the river. Thus resultant velocity, using Pythagoras theorem, V=√(1.2²-0.8²) =√(0.8) =0.8944 m/s Time to cross river =550m/0.8944 m/s =614.9 s =10 minutes 15 seconds, approx. to cross as rapidly a ...
*June 3, 2014*

**Physics - correction**

Power = VI watts
*June 3, 2014*

**Physics**

V=IR I=V/R=45/15000=3*10-3 A. Power = VI joules
*June 3, 2014*

**statistics**

min/max number of people hired =50,80 Best estimate of number of people hired =(50+80)/2=65 Best estimate of people who speak English only = 0.75*65=48.75, or approx. 49 persons Note that sometimes the "best estimate" is interpreted as mean, which often is the best ...
*June 3, 2014*

**Math**

Assuming the question requires the zeroes of Y(x). Multiply by 50 (to get integer coefficients) 50*y(x)=-x²+65x+400=0 Solve by quadratic formula: x=(-65±√(65²+1600))/-2 =5.66 or 70.66 approximately
*June 3, 2014*

**statistics**

If all students take at least one of the subjects, then no one took both, because 84+16=100.
*June 3, 2014*

**Physics**

Area swept by turbine = 2000 m² Wind speed, v = 10 m/s mass of air through turbine, m = Volume of air * density = 2000 m² * 10 m/s * 1.3 kg /m³ = 26000 kg/s Raw power = kinetic energy available /s = (1/2)mv² = (1/2)*26000 kg/s * (10 m/s)^2 J/s = 1.3 MW With...
*June 3, 2014*

**math HELP!!!!!!**

This is an experimental probability project. Ideally you will need a 10-sided die (can get from toy/game stores) in the shape of a duodecahedron (10 identical faces), and proceed as described. The more trials you make, the closer it should approach the expected values, i.e. 10...
*June 2, 2014*

**Physics HELP ME PLEASE**

Newton's second law says "Force = mass × acceleration". Here acceleration = (27-11)/5.4 m/s² mass = 1250 kg So you can find the force accordingly.
*June 2, 2014*

**math :)**

You're welcome!
*June 2, 2014*

**math**

Assuming you mean A= -3(a + b - (1/3)c) when parentheses are used correctly. Divide both sides by -3, and swap sides a+b-(1/3)c = -A/3 -(1/3)c = -A/3-a-b Divide both sides by -(1/3) c = A+3a+3b
*June 2, 2014*

**Physics I NEED HELP BADLY :)**

You're welcome!
*June 2, 2014*

**Physics I NEED HELP BADLY**

Airplane speed = <270,0> (components in the x,y directions) Wind speed 75 km/hr eastwards =<75,0> Resultant speed = <270,0>+<75,0> = <345,0> = 345 km/hr eastwards. Wind speed blowing 75 km/h west Resultant =<270,0>+<-75,0> =<195,0&...
*June 2, 2014*

**physics**

If the acorn fell from rest, equate energies mgh=(1/2)mv² h=v²/2g =100/(2*9.8) =5.1 m Time =v/g =10/9.8 =1.02 s
*June 2, 2014*

**Physics**

Assuming it is a 20 m bridge. Initial vertical velocity = 0 time to reach base = t then t=√(-2Δy/g) =√(2*20/9.8) =2.02 s Horizontal distance =2.02*35 m/s =70.7 m approximately
*June 2, 2014*