# Search results

1. ### Young Modulus

Thank you for your help. I used the quoted value from the textbook but I’ve just spotted that value for copper below it is identical so it could be a mistake in the book. Thanks again
2. ### Young Modulus

I’m fine with part a, answer 3.3 x10^6 but I’m getting 0.00045 for part b when it should be 2.8x10^-4, what am I missing? e = (1500x18)/(1.3x10^11 x 0.000452389)
3. ### Mass of ruler moments

49cm, thank you!
4. ### Mass of ruler moments

The answer is 127.04g. I’m getting close but can’t get the answer. Using 9.81 for gravity, the force where the balance is is 2.10(58146)N As it is balanced 2.10N x 0.29m = W x 0.50m where 0.50 is the centre of mass That gives W = 1.22N = 124.5g?
5. ### Current algebra

Thank you so much that makes sense!

R2/2R?
7. ### Current algebra

(1/2R2 + R)/R?
8. ### Current algebra

1/2 R2/R +R/R Do I have to separate the square now? Sorry, still can't see how I'm going to get the 2/3. Really appreciate your help so far
9. ### Current algebra

Ok so ((RxR)/(R+R)) + R (2R/2R) + R? I don't think that's right but don't understand how I would get the same denominator either
10. ### Current algebra

I think it's (R1xR2)/(R1+R2) for the parallel part then (R1xR2)/(R1+R2) + R to add the series part in but don't know how to combine those?
11. ### Current algebra

Homework Statement An electric circuit consists of 3 identical resistors of resistance R connected to a cell of emf E and negligible internal resistance. What is the magnitude of the current in the cell? (in the diagram two of the resistors are in parallel with each other then the other in...
12. ### Electromagnetic Induction and a coil of wire

The magnetic field that is oriented perpendicularly through a 9.2 cm diameter coil of wire drops from 6.4 T to 6.1 T in 0.076 seconds. What is the emf induced in the coil? Trying to answer this. My question is, if they are perpendicular then does that mean that cos90 makes phi = BAcos theta...
13. ### Doppler effect speed of sound

Excellent! Thank you so much for your help! :)
14. ### Doppler effect speed of sound

f'us=fv-f'v f'us =v(f-f') v=f'us/(f-f') Is that right?
15. ### Doppler effect speed of sound

It's definitely v I need to find. According to my text book us is the moving source velocity. In the other equation it uses uo as moving observer velocity.
16. ### Doppler effect speed of sound

But I'm solving for v?
17. ### Doppler effect speed of sound

Oh yes, sorry. f'v + f'us = fv I still can't see how I set it down to just one v without somehow cancelling both out along the way?
18. ### Doppler effect speed of sound

Multiply by it giving this? f'v+fus = fv
19. ### Doppler effect speed of sound

Yes I know I have us but there are two v's in the equation and I don't know how to rearrange it to get one v on its own?
20. ### Doppler effect speed of sound

Homework Statement Problem: a car is moving away from a stationary observer at 25ms^-1. It emits a frequency of 810Hz and the observer hears an apparent frequency of 762Hz. What is the speed of sound in air at that time? Homework Equations The equation for a source moving away is f' =...
21. ### Determine its speed immediately before landing

Homework Statement Please could someone check if I have got this right? Many thanks The question: An object of mass of 1000kg leaves a 64m high cliff at 100 ms-1 before descending to the ground. Ignoring air resistance, determine its speed immediately before landing. Homework...
22. ### Current in the cell

Got it! Many thanks
23. ### Current in the cell

If R=5ohms 1/5+1/5=0.4 1/0.4 = 2.5 ohms in parallel 2.5 + 5 = 7.5 ohms total If v is 10v I = v/R = 10/7.5 = 1.333333
24. ### Current in the cell

Trying to work out how to do this. I know the answer is B but don't know how. Internal resistance is negligible so I assume I just use I =V/R. I've tried using sample values for R eg 5 and V =10V giving I as 1.3 but am no closer to 2/3. What am I missing?
25. ### Attenuation and power loss

I'm revising attenuation and power loss logarithmic equations. The exam formula I'm given is attenuation = 10 log (I1/I2) I'm trying to confirm what each I stands for. Some of the examples I'm looking at seen to give input/output power, some seem to reverse it. Which is right? What do they...
26. ### On a cliff edge!

Lucy stands on the edge of a vertical cliff and throws a stone vertically upwards. The stone leaves her hand with speed 15m/s at the instant her hand is 80m above the surface of the sea. Air resistance is negligible and the acceleration of free fall is 10m/s/s. First part is to calculate the...
27. ### Percentage Uncertainty

Thank you everyone. I'd gone with fractions rather than whole values. I can see where things went wrong now. Many thanks!
28. ### Percentage Uncertainty

Two lengths, a and b, are measured to be 51+/-1cm and 49+/-1cm respectively. In which of the following is the percentage uncertainty the largest? A a+b B a-b C a x b D a/b The answer should be b but I can't figure out why. I know that for / and x you add the percentage errors so if the error...
29. ### Zero electric field strength

Thank you, that's a really helpful way to picture it. I can see how it would be solved as a multiple choice question without calculations now. Thanks.
30. ### Zero electric field strength

Thanks for your help but I still don't understand. The answer is D but I can't see how you would know that with no numbers apart from the charges. I've tried calculating E using sample distances and get no where near zero. I want to understand the physics and the algebra but neither are making...