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Posts by Scott

Total # Posts: 2,433

algebra
thanks for the catch, Reiny too late to be working on this stuff

algebra
(90 / c) + [130 / (c + 20)] = 4 90 c + 180 + 130 c = 4 c^2 + 80 c c^2 - 35 c - 45 = 0 use quadratic formula to find c

6 grade math area perimeter
area looks good perimeter might be 16 ... check it

6 grade math area perimeter
looks good

Physics
it accelerates for 4 s ... up to 8 rad/s then spins for 11 s ... 88 rad the ave vel during acceleration is ... ) + 8) / 2 = 4 rad/s ... spins 16 rad 104 rad total ... divide by 2? to find revolutions

calculus
the friend's distance north is 30 t your distance east is ... 40 - 20 t it's a right triangle use Pythagoras to find the hypotenuse ... which is the distance find the minimum - with respect to t

Physics
the centripetal force (m v^2 / r) is equal to the gravitational force ... G M m / r^2 v^2 = G M / r ... = 6.67E-11 * 5.98E24 / 7.12E6 the period is the speed divided into the orbital circumference

Physics , static fluids
the ice is 92% as dense as the water so 92% of the block is submerged when it floats that leaves 8% exposed

Algebra
s + L = 40 s + 6 = L subtracting the equations ... eliminating s L - 6 = 40 - L

Physics
the supports each exert 98 N to support the plank one support exerts [490 N * m / 3] to support the person the other support exerts ... 490 N - [490 N * m / 3]

Physics , static fluids
the buoyancy force is the difference in the air weight and immersed weight

Physics , static fluids
hello (again) 8.6 meters is 860 cm if you picture a stack of 860 cm cubes of water, what is the force at the bottom? ... 860 gm * g ... this is the force on one cm^2 .86 kg * 9.8 m/s^2 = f a Pascal is one Newton per m^2 ... a kPa is .001 N per cm^2

Physics
you can use the density of water and the depth to find the pressure the "rule of thumb" for diving is one atmosphere for every ten meters of depth

Physics
e = 1/2 k x^2 ... (kind of like KE) 2.0 = 1/2 * 100 * x^2

Physics
look up Doppler shift formula

Maths
2 = (1 + .06)^t log(2) = t log(1.06) t = [log(2)] / [log(1.06)]

Algebra 2 (Please help Ms. Sue!)
use synthetic division

Algebra
(d / 55) + (d / 35) = 50 - 10

Physics
momentum is conserved find the momenta in x and y for the two decay products the two y momenta add to zero, and the two x momenta equal the original add the vectors to find the 234Th velocity

pre calc
100% - 30% = (1/2)^(2 / h) log(.7) = (2 / h) log(1/2) h = 2 log(1/2) / log(.7) (after a week) = (1/2)^(7 / h)

Algebra
it stops at the top, so the average velocity is ... (103 + 0) / 2 gravitational acceleration is 32 ft/s^2 , downward so the time to reach the peak is ... 103 ft/s / 32 ft/s^2 r * t = d

Physics
momentum is conserved, so the truck's loss is the car's gain 7500 kg-m/s / 750 kg = ?

physics
radio waves travel at the speed of light (c) ... 3E8 m/s the distance from Venus to Earth depends on where each planet is in its orbit around the Sun

technical drawing
85 m is 85000 mm 85000 mm / 10000 = ?

science
x + y = 10 3.1 x + 2.5 y = 25 solves easily by inspection (observation)

physics
6000 Nm/s = 6 kw

Physics
the object displaces 1/5 of its weight in water, so it is 5 times the density of water the weight change in the other liquid is 2/3 of the change in water, so the other liquid is 2/3 the density of water

Chemistry
the Ar will effectively be "squeezed" into 80% of its previous volume this will increase the tank pressure to 125% of the original the pp of Ar is 80% of the total the pp of nitrogen is 20%

Physics
F accelerates the three boxes equally since C is half of the total system mass, F equals twice the force on C

physics
the initial vertical velocity is ... 50 m/s * sin(37º) the (vertical) freefall equation is . h = 1/2 g t^2 + [50 sin(37º)] t + 55 plug in zero for h (ball on ground) and solve for t (use quadratic formula) the horizontal velocity is ... 50 m/s * cos(37º) ... ...

math
the intercepts are points with x and y coordinates for x-intercepts, the y coordinates are zero...but they still exist

Physics
avg vel = (14 + 0) / 2 = 7 rev/s stop time = 1/7 s distance = 1/2 a t^2 ... 1 = 1/2 * a * (1/7)^2

Maths
6 pts total per event 24 pts total awarded...so 4 events Betty has three 1st's and a 2nd Cathy has a 2nd and three 3rd's

physics
momentum (as usual) is conserved .05 * v = (5 + .05) * 10

applied physics
g = -980 cm/s^2 the object reaches its peak at 2 s average velocity is 980 cm/s ... so peak height is 1960 cm time up equals time down

Physics
KE = 1/2 m vB^2 6 KE = 1/2 * m/2 * vA^2 12 = (vA / vB)^2

Physics
twice the force, twice the stretch

Math
what design?

Algebra
the general equation is ... x = a(y - k)^2 + h the vertex is at the origin, so h and k are both zero a = 1 / 4p ... where p is the distance from the vertex to the focus b) the center depth is the value of x at the edges of the dish (where y equals ±7)

Physics
the acceleration (j) of the jet and gravitational acceleration (g) are two sides of the triangle j / g = tan(25º) ... j = 9.8 m/s^2 * tan(25º) multiplying j by 11 s will give the takeoff speed

Psychics
d = 1/2 a t^2 88.3 = 1/2 * 23.6 * t^2

Math
your "weird" answer is correct

Math
An = [10 * 3^(n-1)] + 1

Technology
the moments about the fulcrum must be equal for balance moment = mass * distance from fulcrum

university physics
momentum is conserved with the pellet/block find the velocity of the pellet/block the KE of the p/b is the work that compresses the spring 1/2 m v^2 = 1/2 k x^2

Differential calculus
the general vertex form is ... y = a(x - h)^2 + k ... (h,k) is the vertex a = 1 / 4p ... p is the distance from the directrix to the vertex

Trig
use Pythagoras (a^2 + b^2 = c^2) to find the angle functions then use the trig identity to find the tangent

Advanced physics
the period of the swing (pendulum) is related to its length the speed is not a factor

Algebra
a = 2 b 3(a + b) = 90

Chemistry
an interesting question will probably make for a lively class discussion a couple of pertinent facts ... normal exhaled air is about 15% O2 ... humans can "survive" in air down to about 6% O2

Physics
the work (energy) is equal to the KE of the object f d = 1/2 m v^2 123 * 45.6 = 1/2 * 10.0 * v^2

Maths
12 ... 4/10

Math (Derivative)
a) y = 6 x^-1 ... dy/dt = -6 x^-2 dx/dt ... dy/dt = (-6 / 64) * 12 b) missing y a typo?

Math
p(p + 1) = 3192 p^2 + p - 3192 = 0

Science
yes certainly if 180º apart

Physics
work (energy) to stop the wagon ... w = 42 * g * .18 * 16 w equals the initial KE of the wagon ... 1/2 * 42 * v^2 = w the speed of the boy is the same as the initial speed of the wagon

Chemistry
you are correct

Maths
eight "3" cards gives 24 ... 7 shy of 31 replace four "3" cards with three "5" cards and a "4" card

Physics
d = 1/2 a t^2 t = ?(2 * d * a)

Physics
the period (of the pendulum) is dependent on the length the speed of the "bob" is not a factor

math- Trigonometry
looks good...TALL lighthouse

Chemistry
.325 L * .05 M/L * 55.8 g/M

Math
time is inversely proportional to the number of machines and directly proportional to the number of raviolis t = 15 min * 15/75 * 6000/500

science
would call this a "trick" question circular path means radial (centripetal) acceleration there is no tangential component

Math
d = 6 233 - 53 = 180 ... so, 31 terms s = (233 + 53) * 31 / 2

Physics
1 kcal = 4184 joules m g h = 300 * 4184 h = (300 * 4184) / (1000 * g)

Physics
the gravitational potential energy becomes kinetic energy m g h = 1/2 m v^2 v = ?(2 g h)

Physics
20º is 1/18 of a circle (20/360) the length of the arc is ... 1/18 * 2 * ? * 1 m

Physics
momentum is conserved the smaller mass is 1/3 of the larger ... so it must have 3 times the speed

Math
check the related questions

Physics
f = m a ... a = f / m a = (33 - 12) / (6 + 15)

physics
time up equals time down h = 1/2 g t^2 = 1/2 * 32 ft/s^2v * (2 s)^2

math
the x-coordinate doesn't change the sign of the y-coordinate is reversed drawing a picture can help

Math
complex roots (zeros with i) occur in conjugate pairs f(x) = (x-6+3i)(x-6-3i)(x^5)

math
i = 7400 * [1 - (1 + .06/4)^(4*4)]

algebra
try again on the 1st one the slope formula does work

physics
the frictional force is ... 5 * 9.8 * .4

Physics: Centre of Mass
(4 * 4) + (8 * 5) > 7 * 5 ... so the CM is > 0 [4*(4-x)]+[5*(8-x)]-[7*(5+x)] = 0

Math
Tom has a 40 km head start ... 80 km/h * .5 h Cindy is catching up at 20 km/h ... 100 km/h - 80 km/h

Physics
the velocity is the vector sum of the horizontal and vertical components horizontal ... 88 m / 3.8 s vertical ... time up equals time down ... (3.8 s / 2) * 9.8 m/s^2 the max height is half the initial vertical component, multiplied by half the flight time

Math
distributing the 10 ... 40x + 30 - 9x

Math
undefined slope means the line is vertical the equation is of the form ... x = ?

Physics
a = v^2 / r r = v^2 / a = (54 m/s)^2 / 90 m/s^2

Physics
the object is moving at 20 m/s when the force is removed, the object will be decelerated to a stop (over some distance) by friction find the frictional force (m * g * .2) find the deceleration ... a = f / m find the stopping time ... t = v / a = 20 / a find the stopping ...

pre-calc.
100 = 10^2 10 = 10^1 logarithms are exponents -- powers of some base regardless of the base, the logarithm of 100 will always be twice the logarithm of 10

Pre-Calc
the values for sine and cosine are limited to the range ±1

physics
h = 1/2 g t^2 40 = 1/2 * 9.8 * t^2

Physics
gravity follows an inverse square relation two radii above the surface is three times the distance from the center (of mass) to the surface so the force would be ... g / (3^2)

physics
Pi * Vi / Ti = Pf * Vf / Tf the T is absolute (Kelvin) temperature

physics
you're adding two vectors 2^2 + 4^2 = s^2

Physics
need the drawing for a solution or, at least, more data

Physics
(b) f = m a ... a = f / m = 900 / 1800 a = .5 m/s^2 so it takes 40 s to stop ... 20 / .5 ave velocity is ... (20 + 0) / 2 distance = v * t

Algebra
.12 x + .10(7500 - x) = 890 .02x + 750 = 890

Science Psysics
the gravitational potential energy at the top of the ramp becomes kinetic energy at the bottom of the ramp (minus the work done by friction) m g h - f d = 1/2 m v^2 [6 * 9.8 * 3.5 sin(31º)] - (17 * 35.) = 1/2 * 6 * v^2

Algebra 2
x^2 - 8x + 14 = 0 use the quadratic formula to find x x = {8±?[64-(4 * 1 * -14)]} / (2 * 1)

Algebra 2
use the quadratic formula to find the value(s) of x

physics
momentum is conserved (1200 * 14) + (2000 * 25) = ... (1200 + 2000) * v

Chemistry
8 half-lives 625 * (1/2)^8

Chemistry
3 half-lives m * (1/2)^3 = 6

Chemistry
2 days (48 hr) is 8 half-lives 10.0 * (1/2)^8

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