Thursday

December 18, 2014

December 18, 2014

Total # Posts: 23

**math**

i am between 21 and 34 you say name when you count by fives from zero
*December 17, 2013*

**Chemistry**

If you have a list of acids or bases and their conjugate salts, and are asked which pairs create the best buffer, how would you know which are best?
*June 24, 2008*

**chemistry**

We're studying acids and bases; the question states that 50mL of 0.1M HNO3 solution is mixed with 25mL of 0.1M NaOH. What is the pH? I thought that I would use the Henderson-Hasselbach equation; but my answer does not match the one give in the solution. Any help?
*May 23, 2008*

**CHEMISTRY**

I am struggling with organizing stoichiometry problems; I know how to solve them after they're set up. Here is an example: "An organic compound with a FW of 417 was analyzed for ethoxyl {CH3-CH2O-} groups with the rxn: ROCH2CH3 + HI --> ROH +CH3CH2I CH3CH2I + Ag + ...
*May 16, 2008*

**Physics**

Two point charges lie on the x axis. A charge of + 6.5 µC is at the origin, and a charge of -1.5 µC is at x = 10.0 cm. What is the net electric field at x = -2.0 cm? I found the electrical field for each charge using the equation E= k(q)/ r^2. My calculations were...
*July 7, 2007*

**physics**

At a recent rock concert, a dB meter registered 112 dB when placed 1.70 m in front of a loudspeaker on the stage. (a) What was the power output of the speaker, assuming a hemispherical radiation of the sound and neglecting absorption in the air? (b) How far away would the ...
*June 18, 2007*

**physics**

A 64.0 kg person stands on a lightweight diving board supported by two pillars, one at the end of the board, the other 1.20 m away from the end. The pillar at the end of the board exerts a downward force of 829 N. How far from the pillar at the end of the board is the person ...
*May 31, 2007*

**Physics**

A neutron collides elastically with a helium nucleus (at rest initially) whose mass is four times that of the neutron. The helium nucleus is observed to rebound at an angle '2 = 41° from the neutron's initial direction. The neutron's initial speed is 5.6 105 m/...
*May 30, 2007*

**physics**

An explosion breaks an object into two pieces, one of which has 3.20 times the mass of the other. If 8000 J were released in the explosion, how much kinetic energy did each piece acquire? I started with using KE = (1/2)mv^2 and m1v1 = m2v2. Then (1/2)m1(v1)^2 + (1/2)m2(v2)^2...
*May 29, 2007*

**physics**

A 85 kg trampoline artist jumps vertically upward from the top of a platform with a speed of 3.5 m/s. How fast is he going as he lands on the trampoline, 3.0 m below? If the trampoline behaves like a spring of spring constant 5.2 x 10^4 N/m, how far does he depress it? My ...
*May 28, 2007*

**physics**

A person is to be released from rest on a swing pulled away from the vertical by an angle of 15.8°. The two frayed ropes of the swing are 2.75 m long, and will break if the tension in either of them exceeds 350 N. What is the maximum weight the person can have and not ...
*May 24, 2007*

**physics**

A 2.0kg box rests on a plank that is inclined at an angle of 65° above the horizontal. The upper end of the box is attached to a spring with a force constant of 25 N/m. If the coefficient of static friction between the box and the plank is 0.17, what is the maximum amount ...
*May 21, 2007*

**physics**

A block of mass m1 = 4.50 kg sits on top of a second block of mass m2 = 13.9 kg, which in turn is on a horizontal table. The coefficients of friction between the two blocks are µs = 0.300 and µk = 0.100. The coefficients of friction between the lower block and the ...
*May 21, 2007*

**physics**

Seatbelts provide two main advantages in a car accident: (i) they keep you from being thrown from the car, and (ii) they reduce the force that acts on you during the collision to survivable levels. The second benefit can be illustrated by comparing the net force exerted on the...
*May 17, 2007*

**physics**

A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 9.50 m/s at an angle of 24.0° below the horizontal. It strikes the ground 5.00 s later. (a) How far horizontally from the base of the building does the ball strike the ...
*May 16, 2007*

**physics**

A Coast Guard cutter detects an unidentified ship at a distance of 18 km in the direction 16.2° east of north. The ship is traveling at 22.5 km/h on a course at 36.2° east of north. The Coast Guard wishes to send a speedboat to intercept the vessel and investigate it. ...
*May 16, 2007*

**physics**

A firefighter at street-level, 55.0 m away from a burning building, directs a stream of water from a fire hose at an angle of 35.0° above the horizontal. If the speed of the stream is 50.0 m/s, at what height will the stream of water strike the building? I started by ...
*May 16, 2007*

**physics**

A football is thrown horizontally with an initial velocity of (16.5 m/s). Ignoring air resistance, the average acceleration of the football over any period of time is (-9.81 m/s2). Find the magnitude and direction of the velocity at this time and direction (as an angle) below ...
*May 15, 2007*

**physics**

You are riding on a jet ski at an angle upstream on a river flowing with a speed of 2.8 m/s. Suppose the jet ski is moving at a speed of 18 m/s relative to the water. (a) At what angle must you point the jet ski if your velocity relative to the ground is to be perpendicular to...
*May 14, 2007*

**physics**

A football is thrown horizontally with an initial velocity of (16.5 m/s). Ignoring air resistance, the average acceleration of the football over any period of time is (-9.81 m/s2). (a) Find the velocity vector of the ball 1.62 s after it is thrown. (b) Find the magnitude and ...
*May 14, 2007*

**physics**

A ball is thrown upward from the top of a 27.0-m-tall building. The ball's initial speed is 12 m/s. At the same instant, a person is running on the ground at a distance of 31.2 m from the building. What must be the average speed of the person if he is to catch the ball at ...
*May 13, 2007*

**physics**

A car is behind a truck going 23.0 m/s on the highway. The driver looks for an opportunity to pass, guessing that his car can accelerate at 2.2 m/s2, and he gauges that he has to cover the 24.0 m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more ...
*May 13, 2007*

**physics**

Driving along a crowded freeway, you notice that it takes a time t to go from one mile marker to the next. When you increase your speed by 4.0 mi/h, the time to go one mile decreases by 11 s. What was your original speed? I used the equation V=d/t; I rearranged it to V=(1/t-11...
*May 13, 2007*

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