Wednesday

July 1, 2015

July 1, 2015

Total # Posts: 3,034

**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*

**Precalculus check answers help!**

Were these right???????
*May 31, 2012*

**Physics(Please respond)**

I did the math wrong, I got 103 now.
*May 30, 2012*

**Physics(Please respond)**

Is that correct?
*May 30, 2012*

**Physics(Please respond)**

so on the left side of the equation the mass is gone and on the right side the mass and gravity is gone. So the anwser would be 784h = 1800 h=2.2
*May 30, 2012*

**Physics(Please respond)**

a rollar coaster is 80m high and has a 50kg car at rest. Ignore air resistance and friction. If the speed of the car is 60m/s what is the height? 0+50(9.8)(80) = 1/2(50)(vf^2) + (60)^2 + 50(9.8)(h). Is this equation correct?? If so I do not know how to solve for h since on the...
*May 30, 2012*

**Physics(Please respond)**

so m=1320kg and v=3.32^2 but what is r and mg?
*May 29, 2012*

**Physics(Please respond)**

1) A 1320 kg demolition ball swings at the end of a 34.3 m cable on the arc of a vertical circle. At the lowest point of the swing, the ball is moving at a speed of 3.32 m/s. Determine the tension in the cable. F=ma (34.3)(3.32) = 113.87 Ia this correct?
*May 29, 2012*

**Physics(Please help)**

A jet flying at 106 m/s banks to make a horizontal circular turn. The radius of the turn is 3810 m, and the mass of the jet is 2.40 × 105 kg. Calculate the magnitude of the necessary lifting force. Would I use the equation Fc=mv^2 / r ??
*May 29, 2012*

**Physics(Please help)**

1) A box is sliding up an incline that makes an angle of 14.0 ° with respect to the horizontal. The coefficient of kinetic friction between the box and the surface of the incline is 0.176. The initial speed of the box at the bottom of the incline is 3.72 m/s. How far does ...
*May 29, 2012*

**Physics(Please respond)**

A golfer hits a shot to a green that is elevated 3.0 m above the point where the ball is struck. The ball leaves the club at a speed of 17.4 m/s at an angle of 35.0¢ª above the horizontal. It rises to its maximum height and then falls down to the green. Ignoring air ...
*May 29, 2012*

**Physics(Please respond)**

A golfer, standing on a fairway, hits a shot to a green that is elevated 5.33 m above where she is standing. If the ball leaves her club with a velocity of 48.0 m/s at an angle of 35.7 ° above the ground, find the time that the ball is in the air before it hits the green...
*May 28, 2012*

**Physics(Please respond)**

I meant (17 sin 35)^2
*May 28, 2012*

**Physics(Please respond)**

so for vy I would do (17.4 sin 35) - 2(9.8)(3) ??
*May 28, 2012*

**Physics(Please respond)**

A golfer hits a shot to a green that is elevated 3.0 m above the point where the ball is struck. The ball leaves the club at a speed of 17.4 m/s at an angle of 35.0¢ª above the horizontal. It rises to its maximum height and then falls down to the green. Ignoring air ...
*May 28, 2012*

**Physics(Please respond)**

so is 79.2 kg the value for mass(m) or mg?
*May 28, 2012*

**Physics(Please respond)**

A 79.2-kg person stands on a scale in an elevator. What is the apparent weight when the elevator is (a) accelerating upward with an acceleration of 1.92 m/s2, (b) moving upward at a constant speed, and (c) accelerating downward with an acceleration of 1.89 m/s2 I was going to ...
*May 28, 2012*

**Physics(Please respond)**

A golfer hits a shot to a green that is elevated 3.0 m above the point where the ball is struck. The ball leaves the club at a speed of 17.4 m/s at an angle of 35.0¢ª above the horizontal. It rises to its maximum height and then falls down to the green. Ignoring air ...
*May 28, 2012*

**Physics(thank you for the help)**

A hot-air balloon is rising upward with a constant speed of 2.45 m/s. When the balloon is 3.22 m above the ground, the balloonist accidentally drops a compass over the side of the balloon. How much time elapses before the compass hits the ground? I know that average speed ...
*May 27, 2012*

**Physics(Please respond)**

1) A cave explorer drops a stone from rest into a hole. The speed of sound is 343 m/s in air, and the sound of the stone striking the bottom is heard 1.33 s after the stone is dropped. How deep is the hole? I did 343 / 1.33. Is this correct? Physics(Please help) - drwls, ...
*May 27, 2012*

**Physics(thank you for the help)**

I do not know how to solve for a ratio.
*May 27, 2012*

**Physics(thank you for the help)**

1) A baby elephant is stuck in a mud hole. To help pull it out, game keepers use a rope to apply a force FA. By itself, however, force FA is insufficient. Therefore, two additional forces FB and FC are applied. Each of these additional forces has the same magnitude F. The ...
*May 27, 2012*

**Physcis(Please help)**

A pilot flies her route in two straight-line segments. The displacement vector A for the first segment has a magnitude of 254 km and a direction 30.0o north of east. The displacement vector for the second segment has a magnitude of 178 km and a direction due west. The ...
*May 27, 2012*

**Physics**

1) A jetliner, traveling northward, is landing with a speed of 69.3 m/s. Once the jet touches down, it has 787 m of runway in which to reduce its speed to 13.6 m/s. Compute the average acceleration (magnitude and direction) of the plane during landing (take the direction of ...
*May 27, 2012*

**Physics(Please help)**

When I put 21.792 m/s as my answer my online homework said it was incorrect. Why??
*May 27, 2012*

**Physics(Please help)**

Determine the final speed assuming that the time elapsed since t=0 is 2.4s. Initial velocity is +12m/s acceleration is +3.4m/s^2 I tryed doing 12/2.4 and then 12/3.4 but both of these were incorrect? I am not sure what to do. Thank you.
*May 27, 2012*

**Physics(Please help)**

For some reason when i put in 5.4 as the answer it said I was incorrect. I do not know why.
*May 27, 2012*

**Physics(Please help)**

1) The velocity of a diver just before hitting the water is -11.8 m/s, where the minus sign indicates that her motion is directly downward. What is her displacement during the last 1.06 s of the dive? I know that the formula for displacement is deltaX= x - x0. Would I do -11.8...
*May 27, 2012*

**Physics(Please help)**

So I would set my problem up as (13.3 - X/343)^2 = x/1.76 The only thig I am not sure of is how to solve for the x.
*May 26, 2012*

**Physics(Please help)**

1) A cave explorer drops a stone from rest into a hole. The speed of sound is 343 m/s in air, and the sound of the stone striking the bottom is heard 1.33 s after the stone is dropped. How deep is the hole? I did 343 / 1.33. Is this correct?
*May 26, 2012*

**Physics(Please respond)**

1) A penny is dropped from rest from the top of a very tall building. Assuming the height of the building is 407 m and ignoring air resistance, find the speed with which the penny strikes the ground. I am not sure how to start this. Thank you!
*May 26, 2012*

**Physics(Please help)**

How do you know when to use tan instead of cos or sin?
*May 25, 2012*

**Physics(Please help)**

1) two hot-air balloons are 48.2 m and 61.0 m above the ground. A person in the left balloon observes that the right balloon is 13.3° above the horizontal. What is the horizontal distance x between the two balloons? The left balloon is 48.2m and the right balloon is 61.0m...
*May 25, 2012*

**Physics**

1)A force vector points at an angle of 12.4 ° above the +x axis. It has a y component of +337 newtons (N). Find the magnitude and the x component of the force vector. For the x component I did 337cos(12.4)=329.13 N For magnitude I am not sure what to do.
*May 25, 2012*

**Physics(Please help)**

1) A force vector has a magnitude of 579 newtons and points at an angle 43o of below the positive x axis. Find the x scalar component and the y scalar component of the vector? For the x component I did 579cos(43) = 423.45 N. Is this correct? For the y component I did 579sin(43...
*May 25, 2012*

**Physics(Please help)**

A football is kicked with a speed of 18 m/s at an angle of 65° to the horizontal. How long is the football in the air? Neglect air resistance Would I use the equation y=y0 + voy t -1/2gt^2 ?
*May 25, 2012*

**Physics(Please respond)**

1) Which components remain constant throughout the motion? vx = x component of the velocity vy = y component of the velocity ax = x component of the acceleration ay = y component of the acceleration I know that ax and ay remain constant but I am not sure about vx and vy. Thank...
*May 25, 2012*

**Physics(Please respond)**

There is a diagram of a ball being thrown in a horizontal diection at 30m/s and there is an angle of 48degrees and a side with 4m. How long is the ball in the air? I am confused because I am not sure of the equation. I know that is is something like y = yo + ? - 1/2gt^2 Thank...
*May 23, 2012*

**statistics (college**

An insurance company checks police records (in a city) on 500 accidents selected at random and notes that teenagers were at the wheel in 120 of them. It is desired to test if this information indicate that more than 20% of auto accidents involve teenage drivers in the city. ...
*May 23, 2012*

**Calculus**

Integrate e^((x^3)/2) How do I start? I know that the integral of e^x is just e^x plus C, but what do I do with the ((x^3)/2)? Thanks!
*May 23, 2012*

**pre calculs**

Is that supposed to be f(x)=3x^2-7x-2?
*May 23, 2012*

**Physics**

1) Which components remain constant throughout the motion? vx = x component of the velocity vy = y component of the velocity ax = x component of the acceleration ay = y component of the acceleration I know that ax and ay remain constant but I am not sure about vx and vy.
*May 22, 2012*

**Mathematics I**

Evaluate definite integral from -2 to 0. Integral((x^2)(e^((x^3)/2)dx) Do those parentheses make sense? The power of e is x^3 divided by two. Can someone give me the first step, and I'll see if I can get it from there. I don't want to make you just do the problem for ...
*May 22, 2012*

**physical sciences**

Carbon has an atomic number of 6, which means it contains 6 electrons. To find the number of neutrons, just subtract the atomic number from the mass number. So 14-6 = 8. There are 8 neutrons in an atom of carbon with a mass number of 14.
*May 22, 2012*

**Chemistry**

Why do chloride ions increase corrosion?
*May 22, 2012*

**Physics**

Thank you!!
*May 21, 2012*

**Physics**

Vector A has magnitude of 9.77 units and points due east. Vector B points due north. 1) What is magnitude of B, if the vector A+B points 34.7 north of east? 2) Find magnitude of A+B I am not sure what formulas to use for this. If someone could show me how to start this I will ...
*May 21, 2012*

**Physics(Please check)**

Which equations are dimensionally correct? F=ma E=max X=(1/2)at^3 V=sqrt(2*fx/m) E=(1/2)mv I think that F=ma , E=(1/2)at^3, V=sqrt(2*fx/m) are correct. Would you agree?
*May 21, 2012*

**Physics(Please help)**

thank you!
*May 21, 2012*

**Physics(Please help)**

A force, F1 of magnitude 2.0N and directed due east is exerted on an object is F2=2.0N due north. What is the magnitude and direction of a third force, F3, which must be exerted on the object so that the resultant force is zero? I am not sure how to start this problem!! Thank ...
*May 21, 2012*

**Math**

The circumference of hte front tire is 6ft. How many complete turns does the front wheel make in 30 ft driveway?
*May 18, 2012*

**math**

Compute: The number of combinations of 8 elements taken 3 at a time. The number of permutations of 8 elements taken 3 at at time.
*May 17, 2012*

**Physics(Please check)**

I know the highest point would be 29.4 but I do not know how to get this.
*May 16, 2012*

**Physics(Please check)**

Ok but where did the 9 come from?
*May 16, 2012*

**Physics(Please check)**

1) How long does it take the ball to reach its highest point? I am not sure what I would divide 24 by to find this. 2) How high above the starting point is the highest point? I am not sure how to find this.
*May 16, 2012*

**Physics(Please check)**

A 5-kg ball is thrown straight up in the air with an initial speed of 24m/s. After its release and before it hits the ground when is the ball in free fall? My answer is at all times. Is this correct? Thank you.
*May 16, 2012*

**Physics(Please check thanks)**

Thank you!
*May 16, 2012*

**Physics(Please check thanks)**

Two vectors have magnitudes 4m and 3m. Which choice is not a possible magnitude for their resultant? 3m, 1m, 7m, 12m I chose 12m. Is this correct?
*May 16, 2012*

**Physics(Please respond)**

why is sin negative?
*May 16, 2012*

**Physics(Please respond)**

Vector A has a magnitude 2.4m and direction 130 degrees relative to the positive x-axis. Vector B has magnitude 3.0m and direction 250 degrees relative to the positive x-axis. 1) The resultant R=A+B has magnitude(in m) ? I know the R =2.75m but I am not sure how to get this. I...
*May 16, 2012*

**math**

ok thank you!
*May 12, 2012*

**math**

4 and 505/1000. but how does that help with this?
*May 12, 2012*

**math**

calculate 10^1.27 how do i do this?
*May 12, 2012*

**Math**

One bag contains 5 red marbles, 4 blue marbles, and 3 yellow marbles, and a second bag contains 4 red marbles, 6 blue marbles, and 5 yellow marbles. If Lydia randomly draws one marble from each bag, what is the probability that they are both not yellow?
*May 9, 2012*

**Chemistry**

A patient with untreated diabetes may have a blood concentration of acetone of 20mg/100mL. Determine the molar mass of acetone and use this number to convert this concentration to mol/L. Okay, so I was able to determine the molar mass of acetone (= 58.09g/mol) however, i'm...
*May 3, 2012*