# correct

1. ### What is the correct formula to calculate the angle of vector A = 0i + 1j

I know the angle is 90 degrees. and the formula to calculate the angle of vector A is inverse tan of (Ay / Ax), but Excel returns an error message because Ax is zero. Thanks.
2. ### d'alembert worked example but is trig correct?

Trying to follow another D'Alembert problem (see attached). Can't figure the step where they wrote \delta W_G = -mgR \sin \phi \delta \phi, shouldn't it be \delta W_G = -mgR (1 - \cos \phi) \delta \phi since we are measuring against the vertical force of gravity?
3. ### Is this correct 2 (Different topic)

While waiting for a responce in my earlier post, I looked theough my project one more time and realized that it had anoter big problem. Again I found a formula I'd like to verify, this time with velocity. Velocity^2 = 2 x acceleration x distance Then take the square root of v^2 to get...
4. ### Is this correct?

My formula for a ball rolling down a ramp: (Weight)sin(angle) = a (Weight)cos(angle) = b (Friction) times b = c a - c = d d divided by mass = e e + (5 x 9.8 x sin(angle) ) / 2 = acceleration Is this correct?
5. ### Finding correct gear ratio

I'm trying to find a formula that will allow me to predict what rear end gear I would need to run at a particular oval race track. For instance, Say we run at Daytona, a 2.5 mile track, in a 3400lb car with 850 hp engine turning 8200rpms and tire circumference of 85in and a 1:1 final...
6. ### Correct?

Sorry to bug you guys again. Wanted to make sure I am doing this correctly: A kangaroo jumps vertically to a height of 2.7m. How long was he in the air before returning to earth? I know y0 = 0, y1 = 2.7m and a = -9.80m/s^2 Find velocity with: v^2 = v0^2 + 2a (y1 - y0) v^2 =...
7. ### Is this magnetic field equation correct in material as well?

Or is it only valid in vacuum condition? Segment of straight wire carrying current I (at distance r) dB = u.Idl x r / 4pi . r^2 (I've came across it on a book about Maxwell's Equations.) Does correction have to be made for polarization or magnetization of the material medium? If so, how?
8. ### Are these statements correct?

Hi Everyone: I am writing an essay and would appreciate it if you would check the accuracy of these statements, and let me know how you would correct them, if they weren't accurate. Thanks! Physicists know that the different states of matter are defined at a minute level. A rock is made up...
9. ### Help me understand correct interpretation of Gauss' Magnetic Law

I have been looking at http://www.maxwells-equations.com and they had a different interpretation to what I expected to Gauss' magnetic law. I know this is the divergence operator but for the case of a bar magnet inside a sphere (completely) I imagined that it was the number of magnetic...
10. ### is this the correct way to find impedance

load absorbs 75583 W at a lagging power factor of pf= 0.85. If the current flowing through the load is ix= 0.100A-rms , determine the impedance of the load. VA = 75583 / .85 = 88921 VA = I^2 Z Z = VA / I^2 Z = 88931 / 0.1^2 8.89 x 10^6 ohms
11. ### Is this correct?

Women weighs 100 lb-f on her home planet where acc due to gravity is 35 ft/s^2. How much will she weigh on a planet where the acc due to gravity is 25 ft/s^2?? Using w=mg 100 lb-f = m ( 35 ft/s^2) m = 2.287 lb-f* ft/s^2 So now you use the same formula w= 2.287 lb-f * ft/s^s *(25...
12. ### Problem getting the correct induced current (solution included)

I DO see why the correct solution is correct. What I do not see is why my version is incorrect. Here they are: Correct way: http://i.imgur.com/3SPhU.jpg My way: http://i.imgur.com/RWTbe.jpg Alternatively, you can download them as I am attaching them to this post as well. Basically, I...
13. ### Do I have the correct acceleration??

When a parachut opens, the air exerts a large drag force on it. This upward force is initially greater than the weight of the sky diver and, thus, slows him down. Suppose the weight of the sky diver is 915N and the drag force has a magnitude of 1027N. The mass of the sky diver is 93.4kg...
14. ### Am I correct in setting up this ODE?

The motion of various shaped objects that bob in a pool of water can be modeled by a second order differential equation derived from F = ma. The forces acting on the object are: 1)force due to gravity, 2)a frictional force by water, 3)and a buoyant force based on Archimedes'...
15. ### Is it correct [potential difference between two spheres (mathematical)]

Greetings everyone!! Consider two conducting spheres of radius R carrying equal and opposite charge Q. let the distance between their surfaces be d. We will take the distance from surface of the sphere carrying positive charge. Now the electric field at a point at distance x between the spheres...
16. ### Did I do this correct F=ma to find Vi???

Need help on this. A car whose mass is 2600 kg can produce an unbalanced braking force of 2765N. Calculate the car's initial speed in order to have a stopping distance of 3036.3m. Vi=? So... m=2600kg F=2765N s=3036.3m Vf=0 So I found acceleration of a=F/m = 2765/2600 = 1.06346m/s^2 So I have to...
17. ### Finding correct angle for equal tension

Finding equal tension A 4m length of steel girder is hung horizontally by steel cable each end, the left end is f1 the right end is f2. The steel girder has a mass of 20 kg, 1m from f1 there is a 80 N force hanging down. F2 cable is positioned 30 degree's from the horizontal with a force in the...
18. ### Are my answers correct?

An object starts from rest w/ a constant acceleration of 8m/s^2 along straight line. a)find the speed at the end of 5 sec.------40sec b)the ave. spped for 5 sec interval------20m/s A stone is thrown vertically upward w/ an initial velocity of 49m/s a)How long does it take to reach the highest...
19. ### Are these two kinetic equations correct for the following two problems?

Question 1: Skier travels down straight ramp with constant acceleration of 8.0 ms. Skiers velocity after 5 seconds is 40ms-1 During the time of 5 seconds, what distance is travelled? (this is what i did) V1 = intial velocity V2 = final velocity d = V1 x t + 1/2 x a x t² 0 x 5 + 1/2 x...
20. ### Can someone pls correct me if im wrong thnks :)

You are standing by the side of the street motionless when a car is traveling at a speed of 20m/s passes you. It continues traveling at this speed for 4.0 secs. Then the driver hits the brakes and, with a constant acceleration, comes to rest; traveling 25m while breaking. After 2 secs at rest...