Tuesday
October 21, 2014

Posts by hannah


Total # Posts: 2,889

DR BOB PLEASE HELP CHEM
Consider the reduction of 4-t-butylcyclohexanone. If the procedure calls for 153 mg of 4-t-butylcyclohexanone, what mass of sodium borohydride should be added?
August 19, 2012

CHEMISTRY
thanks :] it is correct. D and C are the answers
August 19, 2012

CHEMISTRY
In TLC, why do you spot multiple times? Select one or more correct answers. A. To fill the capillary almost instantly by capillary action. B. So the developing chamber solvent does not evaporate. C. The higher compound concentration facilitates visualization. D. To acheive a ...
August 19, 2012

Chemistry
Consider the reduction of 4-t-butylcyclohexanone. If the procedure calls for 153 mg of 4-t-butylcyclohexanone, what mass of sodium borohydride should be added?
August 18, 2012

chemistry
There is more than one answer for this problem.
August 18, 2012

chemistry
In TLC, why do you spot multiple times? Select one or more correct answers. A. To fill the capillary almost instantly by capillary action. B. So the developing chamber solvent does not evaporate. C. The higher compound concentration facilitates visualization. D. To acheive a ...
August 18, 2012

Chem
Consider the reduction of 4-t-butylcyclohexanone. If the procedure calls for 153 mg of 4-t-butylcyclohexanone, what mass of sodium borohydride should be added?
August 18, 2012

chem
oh oops i didnt see the e3
August 18, 2012

chem
I am confused so the answer would be .87?
August 18, 2012

chem
-879.6?
August 18, 2012

chem
do this using the appropriate number of sig figs 320.44 − (3104.1/2.6) i got -880 as my answer and it said to check my sig figs. I thought it was all the numbers up to the ones place
August 18, 2012

Chem
Indicate which of the following are exact numbers. the mass of a stapler? i think its inexact because all staplers are different sizes. Is that correct? Also,the mass of a postage stamp. is that inexact? because they can also be diff. sizes?
August 17, 2012

sig figs
I am having trouble with my sig figs Many scientific data are reported at 25°C. What is this temperature in kelvins and in degrees Fahrenheit? I got 3.0e2 degrees kelvin since it will have to have two sig figs but it said it was wrong
August 15, 2012

english-grammar
I am writing an essay and am not sure If I should combine these two sentences with a semi colon or just leave them separate. Please help! (It may take...will be fruitful) I have found that nothing can be accomplished without hard work. It may take a large amount of persistence...
August 14, 2012

Chemistry
Awesome, thank you so much!!
August 12, 2012

Chemistry
Suggest a procedure that could be used to remove lead (II) ions from industrial waste water as a precipitate. Provide an equation and explain your choice.
August 12, 2012

math
Find the error. Sam is finding 9-6+2. Find his mistake and correct it. Steps: First solve the problem. Second, write a summary statement. Third, find Sam's mistake and explain in complete sentences.
July 30, 2012

Chemistry
Describe what hard water is and how a water softening unit works. Provide balanced chemical equations to show how sodium sulphate can remove these ions (Magnesium and Calcium). The first was no problem, but I am having trouble trying to get through the second part balancing ...
July 17, 2012

Math applied/pre-cal
(-8/5)^7/4*(-8/5)^1/4=64/25 Not sure how get this answer . Could please show me the steps.
July 11, 2012

Physics(Please help)
The two strings have the same tension and mass per unit length, but they differ in length by 0.54 cm. The waves on the shorter string propagate with a speed of 41.7 m/s, and the fundamental frequency of the shorter string is 227 Hz. Determine the beat frequency produced by the...
June 22, 2012

Physics(Please check)
A gas, while expanding under isobaric conditions, does 660 J of work. The pressure of the gas is 1.40 x 105 Pa, and its initial volume is 1.70 x 10-3 m3. What is the final volume of the gas? Would I multiply the two values? W = p*dV = p(Vf - Vi)--for isbaric p is constant. ...
June 22, 2012

Physics(Please respond)
A system does 210 J of work on its environment and gains 80.6 J of heat in the process. Find the change in the internal energy of (a) the system and (b) the environment. ÄU = Q - W Where ÄU is the change in the internal energy of the system, Q is the heat/energy ...
June 22, 2012

Physics(Please respond)
A system does 210 J of work on its environment and gains 80.6 J of heat in the process. Find the change in the internal energy of (a) the system and (b) the environment. Physics(Please respond) - Elena, Thursday, June 21, 2012 at 2:33am ÄU = Q - W Where ÄU is the ...
June 21, 2012

Physics(Please help)
A gas, while expanding under isobaric conditions, does 660 J of work. The pressure of the gas is 1.40 x 105 Pa, and its initial volume is 1.70 x 10-3 m3. What is the final volume of the gas? Would I multiply the two values?
June 21, 2012

Physics(Please help)
What is the smallest number of whole logs (ñ = 725 kg/m3, radius = 0.0800 m, length = 3.60 m) that can be used to build a raft that will carry four people, each of whom has a mass of 60.0 kg? I do not know how to start this.
June 21, 2012

Physics(Please check)
A paperweight, when weighed in air, has a weight of W = 6.95 N. When completely immersed in water, however, it has a weight of Win water = 4.26 N. Find the volume of the paperweight. Would I multiply the two values of weight and then by the density of water? 4.26=weightinair-...
June 21, 2012

Physics(Please help)
so I would do log of 4.83 then times 10?
June 21, 2012

Physics(Please help)
The intensity (in W/m2) of one sound is 4.83 times as great as the intensity of another sound. Relative to the quieter sound, what is the intensity level â of the louder sound? I am not sure how to start this. Thank you.
June 21, 2012

Physics(Please respond)
A satellite has a mass of kg orbits the Earth in a circular path with radius 1.0e^7m. What is the period of the satellite? I think I already posted this but I am still confused. My teacher said to use T= 2(pi)r^3/2 / sqrt GmE So I just plugged the numbers in T= 2(pi)(1.oe^7)^3...
June 20, 2012

Physics(Please check, thanks)
Looking through my textbook I found what it was that my teacher said to use. R= Vo^2 Sin 2Q / g So I guess I just have to plug in the numbers; Vo is 25^2 and Q is 40. Correct?
June 20, 2012

Physics(Please check, thanks)
Where did you get 625 and 4.9?
June 20, 2012

Physics(Please check, thanks)
A football player kicks a ball with a speed of 25m/s at an angle of 40 degrees relative to the horizontal. Ignore air resistance. 1) What is the ball's range? R= V0^2 sin Q / g Is this the correct equation to use?
June 20, 2012

Physics(Please, please respond)
so would it be between 90 and 180 or 180 and 270?
June 20, 2012

Physics(Please, please respond)
Vector A has a magnitude of 3.0 m and direction 1o3 degrees relative to the positive x-axis. Vector B has magnitude 5.0m and direction 215 relative to the positive x-axis. For the resultant I did Rx= 3 cos 103 + 5 cos 215 Ry=3 sin 103 + 5 sin 215 Then sqrt Rx^2 + Ry^2 and got ...
June 20, 2012

Physics(Please respond)
A source emits sound uniformly in all directions. There are no reflections of the sound. At a distance of 12 m from the source, the intensity of the sound is 1.7 × 10-3 W/m2. What is the total sound power P emitted by the source? Would I do 1.7e^-3 (12) ?
June 20, 2012

Physics(Please help)
A paperweight, when weighed in air, has a weight of W = 6.95 N. When completely immersed in water, however, it has a weight of Win water = 4.26 N. Find the volume of the paperweight. Would I multiply the two values of weight and then by the density of water?
June 20, 2012

Physics(Please help)
An object is inside a room that has a constant temperature of 295 K. Via radiation, the object emits three times as much power as it absorbs from the room. What is the temperature (in kelvins) of the object? Assume that the temperature of the object remains constant. I thought...
June 20, 2012

Physics(Please help)
A 0.0979-m x 0.215-m x 0.260-m block is suspended from a wire and is completely under water. What buoyant force acts on the block? Would I multiply all the numbers?
June 20, 2012

Physics(Please respond)
An object is solid throughout. When the object is completely submerged in ethyl alcohol, its apparent weight is 15.8 N. When completely submerged in water, its apparent weight is 13.0 N. What is the volume of the object? Would I start by doing 15.8 - 13?
June 20, 2012

Physics(Please respond)
A system does 210 J of work on its environment and gains 80.6 J of heat in the process. Find the change in the internal energy of (a) the system and (b) the environment. I am not sure how to start this. Thank you for the help.
June 20, 2012

Physics
Blood flows through a section of a horizontal artery that is partially blocked by a deposit along the artery wall. As a hemoglobin molecule moves from the narrow region into the wider region, its speed changes from v2 = 0.800 m/s to v1 = 0.422 m/s. What is the change in ...
June 20, 2012

Physics(Please respond)
A system does 210 J of work on its environment and gains 80.6 J of heat in the process. Find the change in the internal energy of (a) the system and (b) the environment. I am not sure how to start this.
June 20, 2012

Physics(Please help)
How did you get 6.378e^6 for R?
June 20, 2012

Physics(Please help)
A satellite of mass 500kg orbits the Earth in a circular path with radius 1.0e^7 m . 1) What is the period of the satellite? I know that the equation is T= 2(pi)r^3/2 / sqrt GmE mE = 5.98e^24 does G = 6.67e^-11 ??
June 20, 2012

Physics(please check)
No it is sin^-1 (1.15/9.8)
June 20, 2012

Physics(please check)
Solve for Q Q= sin^-1 1.5/9.8 I got 8.80 Is this correct? I have a TI-30 calculator and to do the sin^-1 I pushed the 2nd button and then sin. I am not sure if this is correct.
June 20, 2012

physics(Please check)
Actually I think that the direction would be between 180 and 270 degrees since the R is bigger than A but less than B. Would you agree?
June 20, 2012

physics(Please check)
so for the direction of the resultant R would it be between 90 and 180 degrees?
June 20, 2012

physics(Please check)
Vector A has a magnitude of 3.0 m and direction 1o3 degrees relative to the positive x-axis. Vector B has magnitude 5.0m and direction 215 relative to the positive x-axis. 1) The resultant R=A + B has magnitude? I did Rx= 3 cos 103 + 5 cos 215 Ry=3 sin 103 + 5 sin 215 Then ...
June 20, 2012

Physics(Please respond)
There is a rod that is split into two sections. The left side is copper with value of 390, temp of 100 degrees c and the length is 2m. The right side is silver, 420, temp 20 degrees celsuis, and length 1m. I need to calculate the temperature. 390 X 1 X 100-t / 2 = 420 X 1 X t-...
June 15, 2012

Physics(Please check)
Please please respond
June 13, 2012

Physics(Please check)
There is a PV diagram with ABC and the cycle is moving clockwise. segment AB is isobaric BC is isochronic AC cannot be determined The delta U for this is zero and the W=positive. The last questions asks if the heat flow Q is positive, negative, or zero and the answer given is ...
June 13, 2012

Physics(Please check)
There is a rod that is split into two sections. The left side is copper with value of 390, temp of 100 degrees c and the length is 2m. The right side is silver, 420, temp 20 degrees celsuis, and length 1m. I need to calculate the temperature. 390 X 1 X 100-t / 2 = 420 X 1 X t-...
June 13, 2012

Physics(Please respond)
thank you!
June 10, 2012

Physics(Please respond)
A 0.33-kg metal sphere oscillates at the end of a vertical spring. As the spring stretches from 0.12 to 0.26 m (relative to its unstrained length), the speed of the sphere decreases from 5.3 to 4.2 m/s. What is the spring constant of the spring? I know that the formula is F=-...
June 10, 2012

Physics(Please, please check)
A uniform horizontal beam is attached to a vertical wall by a frictionless hinge and supported from below at an angle è = 38o by a brace that is attached to a pin. The beam has a weight of 347 N. Three additional forces keep the beam in equilibrium. The brace applies a...
June 10, 2012

Physics(Please help)
A uniform horizontal beam is attached to a vertical wall by a frictionless hinge and supported from below at an angle è = 38o by a brace that is attached to a pin. The beam has a weight of 347 N. Three additional forces keep the beam in equilibrium. The brace applies a...
June 10, 2012

Physics(please check)
A spring stretches by 0.0226 m when a 4.39-kg object is suspended from its end. How much mass should be attached to this spring so that its frequency of vibration is f = 7.35 Hz? 7.35 = 0.0226(4.39x) Did I set this up correctly?
June 10, 2012

Physics(Please check)
A spring stretches by 0.0226 m when a 4.39-kg object is suspended from its end. How much mass should be attached to this spring so that its frequency of vibration is f = 7.35 Hz? 7.35 = 0.0226(4.39x) Did I set this up correctly?
June 9, 2012

Phsyics(Please respond)
A uniform horizontal beam is attached to a vertical wall by a frictionless hinge and supported from below at an angle è = 38o by a brace that is attached to a pin. The beam has a weight of 347 N. Three additional forces keep the beam in equilibrium. The brace applies a...
June 9, 2012

Physics(Please help)
Some bacteria are propelled by motors that spin hair-like flagella. A typical bacterial motor turning at a constant angular velocity has a radius of 1.9x10-8m, and a tangential speed at the rim of 2.7x10-5 m/s. (a) What is the angular speed (the magnitude of the angular ...
June 9, 2012

Physics(Please check)
A uniform plank of length 5.0 m and weight 225 N rests horizontally on two supports, with 1.1 m of the plank hanging over the right support (see the drawing). To what distance x can a person who weighs 404 N walk on the overhanging part of the plank before it just begins to ...
June 8, 2012

Physics(Please respond)
Some bacteria are propelled by motors that spin hair-like flagella. A typical bacterial motor turning at a constant angular velocity has a radius of 1.9x10-8m, and a tangential speed at the rim of 2.7x10-5 m/s. (a) What is the angular speed (the magnitude of the angular ...
June 8, 2012

Physics(Please help)
A dentist causes the bit of a high-speed drill to accelerate from an angular speed of 1.44 x 104 rad/s to an angular speed of 5.05 x 104 rad/s. In the process, the bit turns through 1.77 x 104 rad. Assuming a constant angular acceleration, how long would it take the bit to ...
June 7, 2012

Derivatives ~ Calculus
If dy/dx = (1 + x)/(xy), x>0, and y=-4 when x=1, then when x=3, y= what?
June 5, 2012

Physics(Please check)
A rectangular plate is rotating with a constant angular speed about an axis that passes perpendicularly through one corner, as the drawing shows. The centripetal acceleration measured at corner A is n times as great as that measured at corner B. What is the ratio L1/L2 of the ...
June 5, 2012

Physics(Please help)
A fan blade is rotating with a constant angular acceleration of +12.4 rad/s2. At what point on the blade, as measured from the axis of rotation, does the magnitude of the tangential acceleration equal that of the acceleration due to gravity? I do not know how to start this.
June 5, 2012

Physics(Please help)
A person is riding a bicycle, and its wheels have an angular velocity of 26.0 rad/s. Then, the brakes are applied and the bike is brought to a uniform stop. During braking, the angular displacement of each wheel is 17.6 revolutions. (a) How much time does it take for the bike ...
June 5, 2012

Physics(Please check)
After 14.6 s, a spinning roulette wheel has slowed down to an angular velocity of 1.22 rad/s. During this time, the wheel has an angular acceleration of -4.51 rad/s2. Determine the angular displacement of the wheel. I did w0= wf + (4.51)(14.6) = 1.22+45.1 46.32(14.6) - (1/2)(4...
June 5, 2012

Physics(Please help)
Three forces act on a hockey puck as it slides across the ice, and it is in equilibrium. The force F is applied at the center and has a magnitude of 25 N. The force F1 is applied at the top edge, and F2 is applied half way between the center and the bottom edge. Find the ...
June 5, 2012

Physics(please check)
thank you, now I understand what I did wrong.
June 5, 2012

Physics(please check)
A 53-N crate is suspended from the left end of a plank. The plank weighs 21 N, but it is not uniform, so its center of gravity does not lie halfway between the two ends. The system is balanced by a support that is 0.30 m from the left end of the plank. How far to the right of ...
June 5, 2012

Physics(Please respond)
so first I have to do equation 2? So 2*pi*17.6 = I am not sure what wo is. Would it be the 26.0?
June 5, 2012

Physics(Please respond)
A person is riding a bicycle, and its wheels have an angular velocity of 26.0 rad/s. Then, the brakes are applied and the bike is brought to a uniform stop. During braking, the angular displacement of each wheel is 17.6 revolutions. (a) How much time does it take for the bike ...
June 5, 2012

Physics(Please help)
Please disregard.
June 3, 2012

Physics(Please help)
1)A 1180-kg van, stopped at a traffic light, is hit directly in the rear by a 753-kg car traveling with a velocity of +1.81 m/s. Assume that the transmission of the van is in neutral, the brakes are not being applied, and the collision is elastic. What is the final velocity ...
June 3, 2012

Physics(Please check)
A car (mass = 1140 kg) is traveling at 27.3 m/s when it collides head-on with a sport utility vehicle (mass = 2380 kg) traveling in the opposite direction. In the collision, the two vehicles come to a halt. At what speed was the sport utility vehicle traveling? I did 1140(27.3...
June 3, 2012

Physics(Please respond)
1)A 1180-kg van, stopped at a traffic light, is hit directly in the rear by a 753-kg car traveling with a velocity of +1.81 m/s. Assume that the transmission of the van is in neutral, the brakes are not being applied, and the collision is elastic. What is the final velocity of...
June 3, 2012

Physics(Please help)
A high-jumper clears the bar and has a downward velocity of -6.00 m/s just before landing on an air mattress. The mass of the high-jumper is 53.7 kg. What is the magnitude and direction of the impulse that the air mattress exerts on her? Assume that upward is the positive ...
June 3, 2012

Physics(please help)
Four very thin rods, each 8.3 m long, are joined to form a square. The center of mass of the square is located at the coordinate origin. The rod on the right is then removed. What are the x- and y-coordinates of the center of mass of the remaining three-rod system? I have no ...
June 3, 2012

Physics(Please help)
1) A man (mass = 80.9 kg) jumps straight down from a bridge into a boat (mass = 482 kg) in which a criminal is fleeing. The velocity of the boat is initially +14.5 m/s. What is the velocity of the boat after the man lands in it? would I subtract the two masses and then ...
June 3, 2012

Physics(Please respond)
1) David has a mass of 86.4-kg and is skating with in-line skates. He sees his 24.8-kg younger brother up ahead standing on the sidewalk, with his back turned. Coming up from behind, he grabs his brother and rolls off at a speed of 2.99 m/s. Ignoring friction, find david'...
June 3, 2012

Physics(Please help, thank you)
1) A student, starting from rest, slides down a water slide. On the way down, a kinetic frictional force (a nonconservative force) acts on her. The student has a mass of 71 kg, and the height of the water slide is 12.0 m. If the kinetic frictional force does -7.4 × 10^3 ...
June 3, 2012

Physics(Please help)
I got 10.68 as my answer but my homework said this was incorrect.Why?
June 3, 2012

Physics(Please help)
A skier slides horizontally along the snow for a distance of 11.9 m before coming to rest. The coefficient of kinetic friction between the skier and the snow is 0.0458. Initially, how fast was the skier going? I do not know how to start this. Thank you. Physics(Please help...
June 3, 2012

Physics(Please respond)
Disregard question. I got the answer. -63072.23
June 3, 2012

Physics(Please respond)
I got 897.45 = 99772.23 + KEf I subtracted 99772.23 from both sides and got -98874.78 for KEf. Did I do this correctly?
June 3, 2012

Physics(Please respond)
1) A roller coaster (398 kg) moves from A (3.82 m above the ground) to B (29.4 m above the ground). Two non-conservative forces are present: friction does -1.82 x 104 J of work on the car, and a chain mechanism does +5.49 x 10^4 J of work to help the car up a long climb. What ...
June 3, 2012

Physics(Please respond)
Disregard question.
June 3, 2012

Physics(Please respond)
so I did (1/2)(83.9)(10.1-6.3) and got 159.41 J.Is this correct?
June 3, 2012

Physics(Please respond)
A water-skier is being pulled by a tow rope attached to a boat. As the driver pushes the throttle forward, the skier accelerates. A 83.9-kg water-skier has an initial speed of 6.3 m/s. Later, the speed increases to 10.1 m/s. Determine the work done by the net external force ...
June 3, 2012

Physics(Please respond)
For the values of mg, m would be 398kg and g is 9.8 correct?
June 2, 2012

Physics(Please respond)
1) A roller coaster (398 kg) moves from A (3.82 m above the ground) to B (29.4 m above the ground). Two non-conservative forces are present: friction does -1.82 x 104 J of work on the car, and a chain mechanism does +5.49 x 10^4 J of work to help the car up a long climb. What ...
June 2, 2012

Physics(Please help)
So for v would I do sqrt(2*11.9*9.8*0.0458) ?
June 1, 2012

Physics(Please help)
A skier slides horizontally along the snow for a distance of 11.9 m before coming to rest. The coefficient of kinetic friction between the skier and the snow is 0.0458. Initially, how fast was the skier going? I do not know how to start this. Thank you.
June 1, 2012

Physics(Please respond)
So for m I would plug in 71kg correct?
June 1, 2012

Physics(Please respond)
so for m
June 1, 2012

Physics(Please respond)
A student, starting from rest, slides down a water slide. On the way down, a kinetic frictional force (a nonconservative force) acts on her. The student has a mass of 71 kg, and the height of the water slide is 12.0 m. If the kinetic frictional force does -7.4 × 103 J of...
June 1, 2012

Physics(Please respond)
A 12-kg crate is pushed up an incline from point A to point B. What is the change in the gravitational potential energy of the crate? Point A is 2.0m and point b is 7.0m I am not sure how to start this.
May 31, 2012

Physics(Please respond)
I did the math wrong, I got 103 now.
May 30, 2012

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