# Search results

1. ### Charge carrier drift velocity of wire

Homework Statement Homework Equations The Attempt at a Solution Current is I = nqvA so drift velocity V is: V = I/nqA Drift velocity for x is: Vx = I/nqA Drift velocity for y is: Vy = 2I/nqA So the ratio of Vx : Vy should be 2:1 since Vy is equal to 2 lots of Vx?? (but correct answer is B)
2. ### Current in a wire

Homework Statement Homework Equations The Attempt at a Solution I know I = nqvA When the pd is applied the surface that is 8cm long, the cross sectional area is 32cm (8x4) but when the pd is applied across the 4cm side, the cross sectional area is now 16cm (4x4) so I has decreased by a...
3. ### Compressions and rarefactions of a wave

Homework Statement Homework Equations The Attempt at a Solution [/B] Slightly confused here. Since this is a displacement-time graph, is it correct to say that at X, since the displacement is zero that it can't be a point of compression because that would imply the air molecules are...
4. ### Circuit with NTC/Voltmeter/Ammeter

Homework Statement Homework Equations The Attempt at a Solution Since resistance of the NTC falls we can say that the total resistance of the circuit has decreased so there is now more current in the circuit, so it's definitely answer B or D. And since X's resistance has fallen, PD...
5. ### Out of phase waves

2. Relevant equation The Attempt at a Solution I can see straight away that the waves are 90 degrees out of phase so pie/2. But how is X ahead of Y? It looks like Y is ahead of X by pie/2.
6. ### Why does a straw look bent in water?

Homework Statement https://www.highlightskids.com/media/kids/highlightskids/images/thumbs/sciQuestions/sq1012_put-a-straw-in-a-glass-of-water_main.jpg [Broken] Homework Equations The Attempt at a Solution From my understanding, this has to do with refraction. Here's my answer: ----- Light...
7. ### Spring constant and energy

Homework Statement Homework Equations The Attempt at a Solution EPE is (0.5)kx^2 Let Y have spring constant of K then X has spring constant of 2K So EPE of Y is (0.50kx^2 which is E So EPE of X must be (0.5)2kx^2 which is kx^2 which is 2E? But correct answer is E/2??
8. ### Kinematic equations for max height

Homework Statement Homework Equations The Attempt at a Solution So (i) was easy enough and I got a time of 0.67 seconds. For (ii), since the horizontal time is 0.67 seconds this means the TOTAL time spent in air is also 0.67 seconds, so to calculate max height we split this time in half...
9. ### Perpendicular forces

Homework Equations The Attempt at a Solution [/B] I was of the understanding that the slope can be calculated as mgsin20 whereas the force acting straight down through the lift is mgcos20 but the answer is mg divided by cos 20??
10. ### Stress/Strain and Youngs Modulus

Homework Statement Homework Equations The Attempt at a Solution The shaded area is a triangle so the area of a triangle for this particular graph is this: 0.5 (Stress)(Strain) which gives: 0.5(F/A)(e/L) so the top would give work done and the bottom would give volume but we're still left...
11. ### Acceleration and speed

Homework Statement Homework Equations The Attempt at a Solution Since at N the gravity is now heading down towards the person in a positive direction it's acceleration is G, where as velocity goes up then comes down towards the person so it's velocity is now negative, thus -V, but the...
12. ### Polarisation of light

Homework Statement Okay so this is a concept that I've been having a lot of problems with recently. I watched a few youtube vids to clear things up so now I'd like to make sure my notes are right. 1) For normal polarised light, the oscillations of a wave are in one plane only which include the...
13. ### Change in Velocity Question

Homework Statement Homework Equations The Attempt at a Solution [/B] Assuming the right direction is positive, it hits the wall and reaches point 2, so to get back to point 1, it's in a negative direction, so it should be MINUS 4m so option A but the correct answer is B?? Or is it to do...
14. ### Acceleration on the Moon

Homework Statement Homework Equations F=ma The Attempt at a Solution I know it's either B or D Weight = mg so let's say mass of ball is 11kg and gravity on moon is 6, so weight would be 66N since acceleration a = F/m and we can say that F=mg therefore a = mg / m which leaves: a=g and...
15. ### Centre of mass/gravity

Homework Statement I'm having a hard time visualising how center of gravity can affect height of an object. Right now I'm looking at an example of an athlete bending their knees to shift their centre of gravity so they can jump higher, and how if during takeoff they push their arms upward they...
16. ### Polarisation (light on water surface)

Homework Statement A student looks at the sunlight reflected off a puddle of water. She puts a polarising (Polaroid) filter in front of her eye. As she rotates the filter the puddle appears darker then lighter. Explain this observation Homework Equations The Attempt at a Solution Here's my...
17. ### Current through voltmeter and ammeter

3. The Attempt at a Solution As temp decreases, the resistance of the thermistor increases...doesn't this mean that the voltmeter will increase too since V=IR? I know that the total resistance of the circuit has increased so less current, but I put down option D but the correct answer is A?
18. ### Current in circuit (bulbs)

Homework Equations Power = VI The Attempt at a Solution [/B] Since lamp M breaks, lamp L gets more of the current so its brightness increases and lamp N's brightness stays the same because the current at point 2 is the same if the other lamp breaks or not, so N's brightness should not be...
19. ### Work done walking up a mountain

Homework Equations I used F=ma to calculate F and pythag theorem to calculate slope lengths The Attempt at a Solution On the left hand side (angle 35) the slope length is 636m, on the right hand side (angle 25) the slope length is 365m. Now, in my notes I know that F=ma and since there is an...
20. ### Centre of gravity question

Homework Statement Homework Equations The Attempt at a Solution For part a) I got t=0.571 seconds For part b) I got s=4.6m But part c) is what I'm stuck on. If his centre of gravity has shifted lower by 50cm, is his time spent in the air greater?
21. ### Hooke's law question

3. The Attempt at a Solution My thinking is that if cross sectional area of the cords increase wouldn't the cords be heavier and thus it would require more work to pull/stretch the device? So more work is done? (But the answers say less work is done because there is a smaller extension/won't...
22. ### Hooke's law and elastic deformation

The Attempt at a Solution [/B] I know that spring A shows elastic deformation since it returned to its original shape once the stress removed and spring c shows plastic deformation and has been permanently extended so it won't return to its original shape. BUT, I'm struggling to complete the...
23. ### Circuit resistance question

Homework Statement I understand part a, but not part B. Homework Equations The Attempt at a Solution For part b) the PD across the resistor is 2V, but we don't know the current so we can't calculate using ohm's law eqn. And because the new resistor's resistance is unkown, how do we...
24. ### Speed from a distance vs. time graph

Homework Statement Homework Equations The Attempt at a Solution I know velocity = distance/time and the steepest gradient means the maximum speed, and the gradient is steepest between 1 and 1.5 seconds with the change in distance being around 40cm so velocity = 40cm/0.5 = 80 cm per second...
25. ### Waves (antiphase)

Homework Statement Homework Equations The Attempt at a Solution For the first part I know the wavelength of light is (1.53 x 414nm) = 633nm But for the second part I'm stumped. Since it's 180 degrees then the waves are in antiphase but I don't understand how to calculate the vertical...
26. ### Electricity current question

Homework Statement Homework Equations The Attempt at a Solution My thinking is that if the resistor's temp goes down then its resistance goes up. This means the current will bypass and ignore this resistor and the current around the circuit will stay the same? But this is wrong. The...
27. ### How to calculate the current of a stream of electrons

Homework Statement The planet Jupiter has a moon Io. Volcanic activity on Io releases clouds of electrons which travel at high speeds towards Jupiter. During a 15 s time period, 2.6 × 10^26 electrons reach Jupiter from Io. Calculate the current. Homework Equations I know current I = Q/t...