# Search results

1. ### Resistivity - Need definition

I am revising for my A levels and I have noticed that a common question on the paper is to define RESISTIVITY. I have looked and looked but found no definitive description or a good definition. I know the formula but is it right to just say that "resistivity is directly proportional to a...
2. ### Force in circular motion

Just wondering if anyone can check over my answer for a question. Q) A 1.7kg object is swung on the end of a 0.6m string in a vertical circle. The object does one revolution every 1.1s. What is the tension in the string at the top of the circle? and the bottom? A) m=1.79kg r=0.6m...
3. ### Geometric progression

just a check of my work please. I have to write an expression for the nth term of this geometric sequence. a1=100 a2=106 a3=112.36 I've worked out the ratio to be r=1.06 I am using the formula un=ar(n-1) so the expression i have come up with is un=100(1.06)(n-1) Is this correct? I have...
4. ### Series and sequence

Just a check of my work please, The topic is series and sequence, Question: The sequence u1, u2, u3,..... where u1 is defined by u1=2 and Un+1 =un+4 Find the nth term, un, of the sequence. I got the answer, u1=-1 u2=-1+4= 3 u3= 3+4 = 7 So: un = 4(n-1)-1 This seems to work but not sure if...
5. ### Amplitude of a wave

Hi, does anyone know how to calculate the amplitude of a wave knowing the frequency and wavelength
6. ### Displacemnet along a spring

Hi guys, Having trouble with a question I need to know the displacment of a point on a spring at certain times. At t=0 point p is at its maximum displacement at 2cm point A is further down the spring at p-A = 0.4m A transverse wave of frequency 5Hz is moving along the spring at...
7. ### Simultaneous polynominals

simultaneous polynominals!! stuck on this coursework question The cubic polynominal f(x)= 4x^3+ax^2+bx+6 has a factor (x-2) when it is divided by (x+1) it has a remainder 0f -15 find the values of a and b I did as follows factor (x-2) f(-2) 4(-2)^3+a(-2)^2+b(-2)+6=0 equals 4a-2b=26...
8. ### Drawing graph of function

I have been asked to draw the graph of the function f(x)= (x+3)/(x-2) I have found where it cuts the y axis by putting x=0 but am unsure of how to find the x value. I found the inverse of f(x)= (x+3)/(x-2) which gave me x= (y+3)/(y-2) then set y=0 which again gave me x=-3 I have checked...
9. ### Composite functions

Im looking for g(f(5)) where f(x) = X^2 - 3x and g(x) = 8 + 2x - x^2 xER and x is greater than or equal to 1 I have first found f(5) (5)^2-3(5) which equals 10 However when i do g(10) 8+2(10)-(10)^2 that gives me a negative number of -72!! Which cant be...
10. ### Inverse Functions

Just want to check that i am doing this question correctly. f(x) = 2x+5 h(x) = 1/x , x \neq0 Find the inverse of fh(x) So first i found the function fh(x) 2*1/x+5 then let y = 2*1/x+5 , x \neq0 now this is the bit i cant rememeber how to do, when i try and make...
11. ### Motion in a straight line tough one

motion in a straight line....tough one ok, a cyclist is travelling at 10ms^-1. he sees trafic lights ahead at 108m. He carries on cycling for a time T before decelerating and stopping at the lights 16.7seconds after he first saw the lights. Calculate T Im a bit stuck because i feel this...

Homework Statement ok the question is as follows. A pilot flying at 45m/s is trying to bomb a target on the ground 15m in diameter. he is at a height of 98m (a)how long does it tke for the bomb to hit the ground? (b)at what horizontal distance does the pilot have to be to release the bomb...
13. ### Intial speed of projectile motion from height

ok im trying to find out how to work out the intial velocity of a projectile dropped from a height h and reaches a distance s. say a ball thrown from a height of 2.8 metres and reaches a distance of 3 metres. I want to be able to work it out WITHOUT having to work out the time. so cant...
14. ### Path of positivley charged particle in electric field

A positivley charged particle is travelling in a straight line with velocity v at a small angle from the horizontal. At a certain instant a constant uniform electrical field is applied in the downward vertical. what is the direction of the charged particle? I figured that the equation for a...
15. ### Light bulb brightness in a circuit

ok revision question fo me, just wanna check my reasonning. which of te bulbs on the circuit of the attatched file will shine more brightly? i think p.............because s and t r and q are in parrellel which is resistance 1/Rs+Rt+1/Rr+Rq where Rp is the sum of the resistance of...
16. ### Pressure from compression

a sample of an idel monotomic gas is intially at a pressure 1.6*10^4Pa and undergoes an adiabatic compression which halves the volume. What is the final pressure? ive been trying to find a way of useing the equation W=-P\DeltaV but am starting to think this is the wrong one as i cant see...
17. ### Simple circuit

Quick question, if i had a circuit of 5 light bulbs whereby 4 were running parellel in a sequence and one was running seperatly, would one be brighter than the others? sorry if it is hard to visulise :)
18. ### Calculate number of molecules

can anyone tell me how i should approach this problem calculate the number of molecules of air in a beach ball of volume 6.0*10^-2m^3. The air is at temperature 35degrees, a pressure of 1.1*10^5Pa and can be trested as an ideal gas. i just want to know what area of classical physics it is
19. ### Orbital period equation

Ok just a quick question trying to work out the orbital period of an asteroid around the sun which has an orbital period 4times that of the earth which is 1.5*10^11m i worked out the radius of the asteroid to be 6*10^11 but cant find the equation for the orbital period. Does anyone know it...
20. ### Differntiate the function

ok just want a check of my work before i send it :) differntiate the function; f(x)=\frac{x(20-x)}{36} so, f'(x)=\frac{(20x-x^2)}{36} f'(x)=\frac{(20-2x)}{36} f'(x)=\frac{(10-2x)}{18} Then....use the composite rule and your answer above to differntiate the function...
21. ### Derive a fraction

Does anyone know how to derive a fraction? I want to be able to differentiate f(x)=\frac{x(20-x)}{36} Ill show you what ive done but think ive just simplified it. f(x)=\frac{x(20-x)}{36} f(x)=\frac{(20-x-x)}{36} f(x)=\frac{(10-x)}{18} Is this correct?...........although not...
22. ### Drawing graph of functions HELP

drawing graph of functions...HELP!! ok, i am going to admit i am TERRIBLE when it comes to drawing graphs of functions. I have no idea what i am doing and kind of need a step by step approach. I really want to learn the best way of doing this as its now a big obstacle in my course. The...
23. ### Angularr speed of disk

A large flat disk with moment of inertia I is spinning with angular speed 18 rad/s a small object lands on the disk and changes the moment of inertia to 1.5I what is the new speed? i used L=I\omega to give me 18*1.5=27 rad/s i used this because L is the angular momentum of the disk and...
24. ### Speed due to gravity

This is a revision question for a test ive got. Just want to check my answer. An asteroid with mass of 1.8*1015kg and radius of 6.7km attracts a spacecraft that has come into its gravitational influence. What speed will the spcaecraft crash into the surface. intial speed of spacecraft is...
25. ### Acceleration due to gravity

sounds simple, im however stuck A planet has a thin isothermal atmosphere at a temperature of 320K and is composed entirely of methane (relative molecular mass of 16) The acceleration due to gravity at the surface is 8.3 m/s/s calcualte the height of the atmosphere. not realy sure where...
26. ### Curling stone coming to rest - friction

This is just a revision question for an exam i have in a couple weeks. I think i kow the answer but just want to double check. a curling stone is released with an instial speed of 3.1 m/s the coefficent of sliding friction between the stone and ice is 0.017 What is the distance the stone...
27. ### Equipotentials around a charge Q

Hi there, im having trouble finding the right equation for a problem ive got. I have a point charge with an equipotential of 40v at 0.4cm. I am suppossed to work out the value of the charge. Ive tried q/4\pi\epsilonr but it doesnt work and i think its because im not putting in a...
28. ### Semi major axis

my question is.......... the semimajor axis of the orbit of jupiter is 7.8*108. If an asteroid has an orbital period half of that of jupiter what is the semi major axis? All i did was times 7.8*108 by 1/2 and got 3.9*108. Seems to simple!!?? any comments much appreciated
29. ### Semimajor axis

my question is.......... the semimajor axis of the orbit of jupiter is 7.8*108. If an asteroid has an orbital period half of that of jupiter what is the semi major axis? All i did was times 7.8*108 by 1/2 and got 3.9*108. Seems to simple!!?? any comments much appreciated
30. ### Ground state of atom

im looking for the 3 principals i need to be employ in determining the electronic structure of the ground state of an atom Ive got Paulis exclusion principle where no 2 electrons in an atom can occupy the same quantum state and hunds rule of the total spin of the electrons always has it...