Hil

Greco I am having a problem with the turntable (gyroscope) problem. The angular speed is 300 radians per second. I tried a couple of formulas including one by you. Maybe I am not converting the units properly. I could use some help. I tried several attemp...

11 years ago

MIT A uniform disc of mass m and radius r is acted upon by three forces. find the magnitude of angular acceleration and the sense of rotation. Three different cases. force F, 3F, 2F. need help, not doing so good.

11 years ago

Hi, Greco. I am using the following formula to solve Ballistic Missile: sqrt(5*G*m_1/4*r_1). Given the following: m_1=5*10^24kg; r_1=6000;alpha=30 degrees;r_2=(5/2)r_1; G= 6.674*10^-11kg/m^3s^-2. I thought I did it correctly using the proper formula. My a...

11 years ago

Consider a rocket in space that ejects burned fuel at a speed of Vex = 1.5 km/s with respect to the rocket. The rocket burns 5% of its mass in 280 seconds. (a) What is the speed V of the rocket after a burn time of 140 seconds (in m/s)? (b) What is the in...

11 years ago

a) Two pendulums consist of a very thin string at the end of which hangs a mass which is much larger than the mass of the rod. In pendulum #1, the rod is made of copper. In pendulum #2, the rod is made of invar. What is the percentage in the period of the...

11 years ago

Is 7.27332*10^-11 meters/second the same as 0.07 nm per second. I believe it is after rounding off. Thanks for your help.

11 years ago

Rank the following three elements in order of increasing Young'sModulus: Ge, Sn, Si. My answer is as follows: Sn<Ge<Si. I am not sure if this correct. Can someone verify. Thanks.

11 years ago

A beam of electrons with momentum p=10^-23 kg m/s passed through a narrow slit of width d=10^-5 m. What is the uncertainty component of the momentum in the x-direction due to the uncertainty principle (approximately)? a. change in p greater or equal to 10...

11 years ago

A closed container with a volume of 8000cm^3 is filled with Xenon gas. the temperature is 273K and the pressure is 2 atm. How many moles of Xenon are in the container? The container is now submerged in boiling water until the gas inside the container is a...

11 years ago

Helium balloons are used regularly in scientific research. A typical balloon would reach an altitude of 40.0 km with an air density of 4.3*10^-3 kg/m^3. At this altitude the helium in the balloon would expand to 540000.0m^3. Find the buoyant force on the...

11 years ago

How is a ratio table used to graph equivalent ratios?

4 years ago

Which equation can be used to find A, the area of the parallelogram shown? A = 5 × 9 A = 4 × 9 A = 12 × 5 × 9 A = 12 × 4 × 9

4 years ago

Thanks, Greco. I figured it out.

11 years ago

I am not sure about (a) I think it is us*d(theta). (b)T/R 1/e^(us*pi)-1 (c)T/R 1/1-e^(-us*pi) I am not 100% positive. Take a look maybe you feel the same way. The tension is opposite.

11 years ago

Hi, Roma. I am having the same problem as you. If I find out I will let you know. I am still trying to solve the problem on the missile.

11 years ago

Hi, Greco. Thanks I got the same answer on the second try.

11 years ago

Can some explain Part d of doppler shift. I used the following: f'= f*(1+speed of observer/speed of sound) f'=450*(1+20/340)=450*1.0588=476.46. This is my last chance. The wind blows toward the observer. Any ideas. Thanks.

11 years ago

Hi Anon or Joe. Rocket Acceleration The following are the variables: Vex=1500m;rocket burns 5% of its mass in 280 seconds. speed v after 140 seconds? V= Vex*ln(1/(1-0.025)) V= 1500*ln(1/(1-0.025)) V= 1500*0.0253178 V=37.97612 m/s a=V/140=37.9767/140=0.271...

11 years ago

I have tried to solve this problem the following way: 5% mass is burned in 280s. 1.5 km/s = 1500 m/s u=fuel speed m/s Solution: V= u*ln(1/(1-p)) 1500*ln(1/0.950) = 76.9399416 m/s a= V/t = 76.9399416/280 = 0.274785506 m/s^2 What is confusing to me what is...

11 years ago

Hi Anonymus, So my question is V= 76.939416 m/s and a=0.2747 m/s^2 correct. Is the other information just trying to through us off? Thanks.

11 years ago

Hi Anonymous, I tried that problem and was unsuccessful. My answer was 8 radians. I knew it was wrong. I put that off to the side. I am just trying to get a passing grade. Thanks for your help. If I learn any thing I will let you know. Also Thanks Greco a...

11 years ago

Hi, Greco. To be honest Questions 1 and the ruler are by far the most difficult for me. when I started the test I knew I was in trouble. I saw this approach: Apply the conservation of energy U= m*g*h cm Ek = m*g* (L/2)+0 l=1/3*m*L Einitial= m*g*(L/2)+0 Ef...

11 years ago

Hi, Unknown. Please show formula for your answer on Venturi flow meter. I would like to compare with mine. Thanks.

11 years ago

Hi, koala. I am having trouble solving for u_s. So far, tan(theta) = 2*(u_s)/(1-u_s)*(u_s+1) u_s=?

11 years ago

Steve, thanks for your help.

11 years ago

a. for copper: 2.65; 1.6%; 0.014%; 0.0014% for invar: 0.00012%; 0.00072%; 0.38%; 0.58% This is what I have done so far: Change in L for copper= 17*10^-6*10^3*16= 0.272m=27.2cm Change in L for invar= 0.9*10^3*16= 0.0144m= 1.44cm b.For copper: 12 sec; 18sec...

11 years ago

Hi, Menes. I an getting a very strange answer, which is incorrect. I must be using the wrong formula. Can you assist. Thanks.

11 years ago

Hi KS, Thanks. 6b) 3.22*10^5

11 years ago

This is what I did with No. 12 Gallium Nitride. A) I said No. B) Wavelength = h*c/E_g = 6.626*10^-34 x 3*10^8/ 3.2 x 1.602 * 10^-19 = 0.388 *10^-6 This is a long shot. Maybe someone can pick up on it.

11 years ago

28 is A and D

11 years ago

9. b) I think the answer is "Both molecules are ionic but the higher melting point has a larger cohesive energy". I ruled out some of the choices, LiF has a strong lattice energy. There are a lot of choices to choose from. This is what I think.

11 years ago

Hi. KS, I have a few more to go. Only one chance left. The graphs, the one on gold, x-ray tube. If you can fill in what you have. 9b is correct.21. is b and both glasses are weaker. Thanks

11 years ago

Hi, KS and Kim. Can you help me with No. 18 electrical measurements. Metal is two orders of magnitude higher at 836 degrees than at 499 degrees C. What is the energy formation for this metal. Thanks.

11 years ago

Hi, KS and Kim. Can you help me with No. 18 electrical measurements. Metal is two orders of magnitude higher at 836 degrees than at 499 degrees C. What is the energy formation for this metal. Thanks. In(100)= H_v/8.314(1/772.15-1/1109.15)

11 years ago

On no. 25. I believe the highest density is Coesite. The others are tricky. Does anyone know. On 26, phases for Cu at 95wt.% I think is 2. At 15wt.% for Cu, I think is 2. For no. 29, I think linear structure has a larger molar volume. Branched structure a...

11 years ago

Thanks Tania. I was making calculation errors and unsure of what they were looking for on the gold problem. I am having he same problem with no 18. I know the formula but getting the wrong answer. Temp = 836 C and 499 C In(100)=H_v/8.314(1/772.15-1/1109.1...

11 years ago

No.29 is correct. No. 18 can you check my math. ln(100)=H_v/8.314*(1/772.15-1/1109.15) ln(100)= H_v/8.314*0.000393 H_v= ln(100)*8.314/0.000393 H_v=ln(100)*21155.2163) H_v=97423.37 joules H_v=97.42337 kilo joules Thanks.

11 years ago

No. 25 This is my answer: lowest density: cristobalite; next lowest: tridymite; next lowest: beta quartz; next lowest: alpha quartz; highest density: coesite. Please verify.

11 years ago

Please Help Me guys!

4 years ago