Tuesday

February 21, 2017
Total # Posts: 1,812

**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)

*November 22, 2016*

**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

*November 22, 2016*

**Physics**

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

*November 22, 2016*

**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

*November 22, 2016*

**technical drawing**

85 m is 85000 mm 85000 mm / 10000 = ?

*November 22, 2016*

**science**

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

*November 21, 2016*

**physics**

6000 Nm/s = 6 kw

*November 21, 2016*

**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

*November 21, 2016*

**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%

*November 20, 2016*

**Physics**

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

*November 20, 2016*

**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) ... ...

*November 20, 2016*

**math**

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

*November 20, 2016*

**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

*November 20, 2016*

**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

*November 20, 2016*

**physics**

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

*November 17, 2016*

**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

*November 16, 2016*

**Physics**

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

*November 16, 2016*

**Physics**

twice the force, twice the stretch

*November 16, 2016*

**Math**

what design?

*November 16, 2016*

**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)

*November 16, 2016*

**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

*November 16, 2016*

**Psychics**

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

*November 16, 2016*

**Math**

your "weird" answer is correct

*November 15, 2016*

**Math**

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

*November 15, 2016*

**Technology**

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

*November 15, 2016*

**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

*November 15, 2016*

**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

*November 14, 2016*

**Trig**

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

*November 14, 2016*

**Advanced physics**

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

*November 13, 2016*

**Algebra**

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

*November 13, 2016*

**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

*November 13, 2016*

**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

*November 13, 2016*

**Maths**

12 ... 4/10

*November 13, 2016*

**Math (Derivative)**

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

*November 13, 2016*

**Math**

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

*November 13, 2016*

**Science**

yes certainly if 180º apart

*November 12, 2016*

**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

*November 12, 2016*

**Chemistry**

you are correct

*November 12, 2016*

**Maths**

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

*November 11, 2016*

**Physics**

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

*November 11, 2016*

**Physics**

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

*November 11, 2016*

**math- Trigonometry**

looks good...TALL lighthouse

*November 11, 2016*

**Chemistry**

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

*November 11, 2016*

**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

*November 11, 2016*

**science**

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

*November 11, 2016*

**Math**

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

*November 10, 2016*

**Physics**

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

*November 10, 2016*

**Physics**

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

*November 10, 2016*

**Physics**

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

*November 10, 2016*

**Physics**

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

*November 10, 2016*

**Math**

check the related questions

*November 10, 2016*

**Physics**

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

*November 10, 2016*

**physics**

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

*November 10, 2016*

**math**

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

*November 9, 2016*

**Math**

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

*November 9, 2016*

**math**

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

*November 9, 2016*

**algebra**

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

*November 9, 2016*

**physics**

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

*November 9, 2016*

**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

*November 8, 2016*

**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

*November 8, 2016*

**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

*November 8, 2016*

**Math**

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

*November 8, 2016*

**Math**

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

*November 7, 2016*

**Physics**

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

*November 7, 2016*

**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 ...

*November 7, 2016*

**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

*November 7, 2016*

**Pre-Calc**

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

*November 7, 2016*

**physics**

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

*November 6, 2016*

**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)

*November 6, 2016*

**physics**

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

*November 6, 2016*

**physics**

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

*November 6, 2016*

**Physics**

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

*November 4, 2016*

**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

*November 4, 2016*

**Algebra**

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

*November 3, 2016*

**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

*November 2, 2016*

**Algebra 2**

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

*November 2, 2016*

**Algebra 2**

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

*November 2, 2016*

**physics**

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

*November 2, 2016*

**Chemistry**

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

*November 2, 2016*

**Chemistry**

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

*November 2, 2016*

**Chemistry**

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

*November 2, 2016*

**Chemistry**

5 / 20 = 1/4 = (1/2)^2 2 half-lives

*November 2, 2016*

**Algebra 2**

3 half-lives 345 * 1/2 * 1/2 * 1/2

*November 2, 2016*

**Need help with math**

people who own both (b) will be counted in both groups (laptop owners and desktop owners) when you count all of the households, the "both" group is only counted once 130 + 30 + 50 + b = 250

*November 1, 2016*

**Mathematics**

the area is side times altitude 30 * 15 = 25 * x

*November 1, 2016*

**Math**

8 oz per cup

*October 31, 2016*

**Science**

switching the electrical polarity also switches the magnetic polarity

*October 31, 2016*

**Science 7**

switching the wires changes the magnetic polarity of the coil

*October 31, 2016*

**algebra 2**

3000 = 2000 [1 + (.038 / 2)]^(2t) ... t is the number of years 1.5 = 1.019^(2t) log(1.5) = 2t * log(1.019)

*October 31, 2016*

**Physics**

the gravitational potential energy becomes work driving the pipe m g h = f d 450 * g * 1.5 = f * .45

*October 30, 2016*

**Math**

y^2 + 5y - 6 = y^2 - 5y + 6 + 8 5y + 5y = 6 + 8 + 6

*October 30, 2016*

**Math**

(x + 2)^2 - x^2 = 44 x^2 + 4x + 4 - x^2 = 44 4x + 4 = 44

*October 30, 2016*

**Math**

28x - 7y = -119 ... add to 1st eqn

*October 30, 2016*

**math**

draw a Venn diagram of three intersecting circles enclosed in a box label the circles S, F, and G S/F/G -- 2 ... these are in all the two way intersections S/F -- 10 + (2) S/G -- 4 + (2) F/G -- 6 + (2) S -- 19 + (2) + (10) + (4) F -- 13 + (2) + (10) + (6) G -- 10 + (2) + (4...

*October 30, 2016*

**Math**

A = 3M A - 3 = 4 (M - 3) = 4M - 12 3M = 4M - 9

*October 30, 2016*

**Math**

18 r^5 = 2/27 9 r^5 = 1/27 r^5 = 3^-3 / 3^2 = 3^-5

*October 30, 2016*

**Math Grade 9**

square rooting implies that the yard is square ... from the result of your answer, this is not the case the "perimeter" in this problem, is only three sides A = L * W = 50 P = L + 2W a good investigation might consist of a table comparing L, W, and P ... remember, ...

*October 30, 2016*

**Algebra**

p + r = 18 35p + 49r = 728 solve the system by substitution or elimination

*October 30, 2016*

**math**

10 is a factor ... ?????0 The hundred thousands and ten thousands digit are the same and are odd ... must be less than 3, and odd ... 11???0 The sum of the hundreds and the thousands digits is 10 ... neither one can be zero The tens digit is a cube number and is one more than ...

*October 29, 2016*

**Physics**

the blocks accelerate at ... 60/18 = 10/3 m/s^2 the force necessary for b ... 15 * 10/3

*October 27, 2016*